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All you want to know about
Heat Waves and Health

Understand the issue

Know the risk factors

Know how to keep yourself and others safe during a heat wave

After the heat wave is over

Understand the issue

Heat waves, also known as heat events, are a series of days that have significantly hotter than normal temperatures or HumidexHumidex is a measure of humidity in the air. Humidity can make heat feel more intense. levels for a geographical region. With climate change, heat waves are becoming more common. They last longer and come with higher temperatures than they used to.

Heat waves can negatively affect anyone’s health. Extreme heat can make certain chronic conditions worse and can cause heat-related illnesses that range from mild to life-threatening.

The good news is that when you’re well-prepared, you can stay safe. Ideally, you start preparing for summer heat waves in the spring, so that when a heat warning is issued, you’re ready and able to protect yourself.

In Southern Ontario, a heat warning is an alert issued when:

  • Daytime temperatures are expected to reach 31°C or warmer for two or more days in a row, with nighttime temperatures expected be 20°C or warmer, OR

  • Humidex values are expected to reach 40°C or higher for two or more days in a row.

Heat warning thresholds can vary according to region and typical temperatures. For a list of heat warning thresholds, see Alerting parameters Environment Canada uses for issuing a Heat Warning.

For local weather alerts, visit Environment and Climate Change Canada (ECCC).

Heat puts stress on the body. It can worsen chronic conditions and cause heat-related illnesses like heat exhaustion and heat stroke. This stress increases with the number of chronic conditions and other risk factors that someone has.

Heat illnesses can affect a person quickly and are mainly caused by over-exposure to heat, over-exertion in the heat, and dehydration. Heat-related illnesses and their symptoms include:

  • Heat rash: Red clusters of small blisters that look like pimples on the skin (usually on the neck, chest, groin, or in elbow creases)
  • Heat edema: Swelling of hands, feet and ankles
  • Heat cramps: Painful muscle spasms, usually in the legs or arms
  • Heat exhaustion: Weakness, headache, nausea/vomiting/diarrhea, thirst, dark urine, intense fatigue
  • Heat stroke: Red and hot skin, dizziness, nausea, confusion, loss of coordination or a change in consciousness. Heat stroke is a medical emergency!

Heat illnesses that progress to heat stroke, or chronic conditions that worsen significantly due to heat, can be life-threatening.

Know the risk factors

During the first couple of days of a heat wave you may feel fine. But then something can happen, and you start to feel worse. A number of things can lead to a heat-related health problem, including:

When you know about these, steps can be taken to keep yourself safe by preventing them from happening or dealing with them when they do happen – see Create a Heat Safety Plan to keep yourself and others safe.

How can unrelenting heat cause a heat-related health problem?

Understanding how unrelenting heat can be dangerous comes down to an important fact: The only way the body can cool off in the heat is to release heat through the skin.

There are 4 ways your body can release heat through the skin:

  • You sweat and the sweat can evaporate (which is limited if the air is humid)

  • You have contact with a cool surface (such as or a cool wet towel around your neck)

  • You are exposed to cool air

  • You have contact with cool water (in a pool, bath or shower)

If you are unable to release heat through your skin, you’re at risk of overheating. Furthermore, the heat can put added strain on your heart because it has to pump blood to your skin (as well as everywhere else) in an effort to cool you down. If your heart can’t keep up, your body temperature may increase.

When your body can’t cool down, chronic conditions can get worse and/or you may experience a heat-related illness such as heat exhaustion or heat stroke. Heat stroke is a medical emergency.

Unrelenting indoor heat is a serious health risk

During extreme heat events, it is a sobering truth that most heat-related deaths occur indoors, because our homes are not able to withstand the outdoor heat.

Research has indicated a safe indoor temperature is up to 26oC, although this can be less if there is high humidity, or if you have multiple risk factors.

  • As the indoor temperature rises above 26oC, it becomes harder for most people – especially older adults – to not overheat.

  • It can take a day or two for indoor heat to increase, so at first you may think you’ll be okay. But once your place has heated up, it can be very challenging to cool it down during a heat wave.

  • Follow the protective measures described in the Heat Safety Plan. If you start to have symptoms of overheating, you may need to find a cooler place to go for several hours, or possibly overnight.

  • Spending some time in air-conditioned spaces during extreme heat events is associated with a reduced risk of death.

  • Assessing whether your (or someone else’s) indoor heat is unsafe—and taking action to get to a cooler place when that happens—is very important to keeping safe during a heat wave. Learn what measures you can take to protect yourself or someone else.

How can humidity contribute to a heat-related health problem?

  • Humidity decreases the ability of the body to cool itself.

  • If the Humidex is 35-39, you should reduce or modify certain types of outdoor exercise, especially if you have risk factors.

  • A Humidex over 40 is extremely high risk: Reduce all unnecessary physical activity. If you don’t, you could get heat stroke.

  • If you have multiple risk factors, you may need to modify your activities at even lower Humidex levels.

  • Monitor how you are feeling and take your temperature.

  • If you are feeling uncomfortable, you need to get out of the heat. Go to an air-conditioned space for at least an hour or two, and if you find yourself getting overheated at nighttime, arrange to stay with a friend or family member or go to the nearest cooling station or other public space that has air conditioning. If you’re not sure where that is, call your local municipality or 211 to find out where you can go to cool down and how to get there.

How does dehydration make you more vulnerable to a heat-related health problem?

  • If you don’t drink enough water when you’re hot, dehydration can set in quickly.

  • Dehydration can decrease your circulating blood volume. When you have less blood volume, it can be hard on your heart. Certain chronic conditions can start to get worse, or heat exhaustion can set in.

  • To prevent becoming dehydrated, make sure you’re drinking enough water. It’s easy to underestimate how much water you need when it’s hot, so take frequent sips even if you don’t feel thirsty. If you’re going outdoors, drink a glass of water before leaving and bring a full bottle of water with you.

  • If you’re passing urine that is darker than usual or haven’t peed for many hours, you may be dehydrated. These are signs that you need to drink more water.

  • Note: Sometimes, in an effort to avoid dehydration, you may drink too much. One sign that may be happening is if you find yourself needing to pass urine frequently. If you drink too much you can wash out sodium in your body. You may want to lower your fluid intake and get something to eat, to replenish the sodium levels in your body.

How can a sunburn lead to a heat-related illness?

  • Sunburns can damage your skin and sweat glands, reducing your body’s ability to stay at a normal temperature and to produce sweat that cools you down. Sunburns can also affect your ability to feel heat and to know when you have overexerted yourself.

  • To manage this, try to avoid going outside when the sun is hot. If you need to go out, apply at least SPF 15-30 sunscreen on exposed areas of your skin before you go out, and reapply it on a regular basis. You should also wear a hat and keep yourself covered with light-coloured clothing.

  • If you go out in the morning or evening when the mosquitoes are out, apply sunscreen first and then insect repellent.

Anyone can develop a heat-related illness, but some people are at higher risk than others. There are many risk factors that can increase your vulnerability to heat, including past history of a heat illness, being in a higher-risk age group, having certain health conditions, certain social factors, as well as the building and surrounding factors where you live.

Who is at risk?
Social factors that increase risk
Buildings and surrounding factors that increase risk

Who is at risk?

  • Infants and children: Extreme heat, and heat-related illnesses, are especially dangerous for infants and young children. Children sweat less than adults and have a higher metabolism, so they get hot quicker. They can also easily lose body fluids and become dehydrated quickly. To learn more about how children are at risk and what you can do to keep them safe, see this resource from Health Canada: Keep children cool! Protect your child from extreme heat.

  • Pregnant women: Hormonal changes and increased metabolism raise body temperature during pregnancy. The body’s natural cooling mechanisms are already working overtime, making pregnant women more vulnerable to heat-related illnesses when the weather is very hot.

  • Older adults: Older adults lose their ability to maintain normal core body temperature because their hearts and their ability to sweat tend to become less efficient with age. They may also have chronic conditions and mobility challenges that can lead to social isolation, all of which are additional risk factors.

  • Outdoor workers: People who work outside in the summer experience increased physical strain with prolonged exposure to heat. They are most at risk during the first heat wave of the season and/or on the first few days of an outdoor job.

  • People who do outdoor activities or sports: People who regularly do outdoor activities (walk, run or cycle), or who are recreational athletes or marathon runners, are under increased physical strain in the heat. They may underestimate their risk from heat and expect to perform at their usual level even when it is hot.

  • People with chronic conditions: Heart disease, chronic lung disease, renal disease, neurologic and psychiatric illnesses are all chronic conditions that can get worse with heat.

  • People taking medications: Some medications can interfere with sweating, thirst, or salt/water balance.

  • People with mobility issues Decreased mobility can be caused by a number of conditions such as severe arthritis of the knee or hip, and other chronic pain conditions such as back pain or chronic fatigue syndrome.

    • During a heat wave and in an increasingly warm indoor environment, people with decreased mobility may have difficulty taking a cool bath or shower or getting to a cooler indoor environment.

    • People with decreased mobility are often homebound and may become socially isolated.

    • This risk can be reduced by having informal support from friends and neighbours as well as home-based health and social services.

  • People who are overweight: People who are overweight are more than three times as likely to have heat exhaustion than those with an average body weight. This is because their bodies produce more heat and have a harder time cooling down.

  • People who consume alcohol: Alcohol can alter your body’s temperature regulation, increase your risk of dehydration, and reduce awareness of your body and your environment. This risk can be partially lowered by decreasing and slowing the amount of alcohol you drink on hot days, and making sure that each drink of alcohol is followed by a drink of water.

Social factors that increase risk

  • Living alone and social isolation:

    • Social isolation is an important risk factor for heat health problems. Most heat-related deaths during heat waves occur in people who live alone and are unable to keep their home cool (due to lack of shade, basement, or air conditioning).

    • Social isolation can arise simply from the preference to not leave home, or from a mental health condition such as anxiety or depression, feeling marginalized, from chronic pain, or decreased mobility.

    • The risk of a heat illness occurring in someone living alone is increased when it’s combined with low income, since they often have reduced access to transportation and lack of air conditioning.

    • This risk can be reduced by informal supports such as having check-in companions (e.g. neighbours or family checking in), in-home health and social services, as well as phone-based services such as Health811.

  • Newcomers (immigrants, refugees or tourists):

    • Newcomers may not be aware that heat waves are a health issue, nor be aware of local alert systems or services available to help keep them safe during heat waves.

    • Some newcomers may have cultural preferences for clothing that place them at increased risk (e.g. dark or multiple layers of clothes) or may simply not have the appropriate clothes and protective gear (like a hat or umbrella).

    • Some people fast as a religious practice (for example, in Islam during the month of Ramadan, there is no eating or drinking from dawn to dusk) which may place them at high risk of dehydration. If Ramadan occurs in the summer, ask your Imam if accommodations can be made to stay hydrated during the day.

  • Low income:

    • There are many factors associated with poverty that increase the risk of developing a heat-related illness. These can include lower levels of education, reduced access to transportation, living in a single room without a bath or shower, lack of air conditioning and ventilation, and/or hesitation to use existing or available resources, such as cooling centres (as they may think they would not be welcome there).

    • This risk can be reduced by calling your municipality for information on where to find a cool environment and how to get there (Ottawa residents can also visit “Places to Cool Off – Interactive Map” for locations in Ottawa). You can also call 211, a 24-hour helpline that can connect you to local cooling centres and other community supports.

  • Unhoused/marginalized housing:

    • If people don’t have their own housing, they may stay with other people, live in shelters or stay outdoors. If they’re in a city they may be exposed to increased heat from the “heat island effect” (as buildings, roads and concrete store heat). They are more likely than those who are housed to have other risk factors, such as chronic conditions, substance use and fewer protective items like hats, light-coloured clothing and water bottles. It may be harder for them to remain hydrated or find transportation to cool public buildings and cooling stations.

    • This risk can be reduced by asking around about where is the best place to get cool or calling 211 for help finding cool space and how to get there. For example, there may be a nearby library or other welcoming public places where you can rest, cool down and refill your water bottle. Eating helps to keep your electrolytes normal. If funds are tight, go to a food bank when it’s not too hot to get water-rich foods, like soups, fruits and vegetables. Don’t hesitate to call 211 to see what services are available such as free water distribution spots, cooling stations, outdoor pools, and how to get there.

  • Other marginalized groups:

    • May include Indigenous people, LGBTQ2S people, people with disabilities, children and youth in care, people living in remote areas, and others.

    • Marginalized groups may be aware of their increased risk but be reluctant to go to cooling stations and public air-conditioned places as they may feel unwelcome. Don’t hesitate to call 211 to see what services and supports are available that may make you more comfortable.

Buildings and surrounding factors that increase risk:

Residences are least likely to have a cool place during a heat wave when they:

  • Have no air conditioning (AC) – this is the biggest factor

  • Have no shade around the building from trees or other buildings

  • Have a flat, dark roof

  • Have no ventilation

  • Are on the second or higher floor of the building, or if they’re single rooms that have no shower or bath

A lack of shade means there’s nothing that is protecting your residence from getting overheated by the sun during a heat wave. In addition, hot air rises. If there is no air conditioning to cool the indoor air and your residence is not in the basement or first floor, you will be in a hotter place than those below you. If you have to walk up to your place, it will place an increased strain on your body just to get home – especially if you have a chronic condition or limited mobility.

Cities can be hotter than rural areas due to the “heat island effect”. The heat island effect is when cities experience much warmer temperatures than nearby rural areas. This happens because of the greater concentration of buildings and roads, which absorb heat from the sun, then store and radiate that heat locally, adding to the temperature of the area.

These risks can be reduced by planning in advance and creating a Heat Safety Plan.

Chronic diseases can worsen during heat. For example:

  • Chronic lung disease and asthma
    Hot air can cause airways to narrow, making it harder for people with COPD to breathe. This increases inflammation and the risk of death. In asthma, hot air can cause hyperinflation (lungs don’t empty before the next breath). Heat can also trap dust, mold, and pollen, triggering asthma. Heat increases ground-level ozone, which irritates lungs.

  • Heart problems
    Heat puts stress on the heart. Dehydration reduces blood volume, making it harder for the heart to send blood to the skin to cool the body. Poor air quality from ozone and particulate matter (e.g. wildfire smoke) puts a further strain on heart function.

  • Kidney disease
    Dehydration during heat waves impairs kidney function and may cause kidney stones. People with kidney disease are at increased risk of acute kidney failure.

  • Neurological conditions
    Conditions like Parkinson’s, Alzheimer’s, seizure disorders, and MS can reduce strength and mobility, making it harder to get to a cool space. This can lead to rising body temperatures.

  • Mental health conditions
    Conditions like depression or schizophrenia may reduce awareness or response to heat risk. People may ignore advice or have fewer coping mechanisms.

  • Note: Many medications for chronic conditions can increase heat risk. Ask your pharmacist if your meds increase heat sensitivity.

Some medications can affect your body’s ability to cool itself in heat. Speak to your pharmacist about whether any of the medications you are taking increase your risk during heat events and follow their advice. (Note: Never stop taking a medication without first speaking to your pharmacist or doctor.)

Below is a list of some medications that can increase your risk in heat (it does not include all medications).

  • Beta-blockers (metoprolol, bisoprolol, carvedilol, atenolol, labetalol, propranolol, nadolol, sotalol)

  • Antiplatelet medications (Aspirin, clopidogrel, prasugrel, ticagrelor)

  • Diuretics (hydrochlorothiazide, chlorthalidone, indapamide, metolazone, furosemide, spironolactone, eplerenone, ethacrynic acid)

  • Anticholinergics, including:

    • Allergy medication: diphenhydramine, chlorpheniramine, brompheniramine, dimenhydrinate, doxylamine, hydroxyzine, carbinoxamine, cetirizine, loratadine, fexofenadine, levocetirizine, desloratadine, bilastine, tupatadine, azelastine

    • Tricyclic antidepressants: amitriptyline, imipramine, nortriptyline, doxepin, clomipramine, desipramine

    • Serotonin selective reuptake inhibitors: paroxetine

    • Antipsychotics: chlorpromazine, clozapine, olanzapine, quetiapine, fluphenazine, loxapine, haloperidol, methotrimeprazine, pericyazine, perpherazine, primozide, trifluperazine

    • Antiseizure: carbamazepine, oxcarbazepine

    • Sleep aids: zolpidem

    • Muscle relaxants: cyclobenzaprine, baclofen, methocarbamol, orphenadrine, tizanidine

    • Incontinence medications: darifenacin, fesoterodine, flavoxate, oxybutynin, propiverine, solifenacin, tolterodine, trospium

    • Gastrointestinal: atropine, belladona, chlordiazepoxide, dicyclomine, dimenhydrinate, diphenoxylate, loperamide, ranitidine, scopolamine, promethazine, prochlorperazine, meclizine, diphenhydrinate

    • Respiratory: pseudoephedrine, theophylline

    • Opioids: morphine, hydromorphone, fentanyl, codeine, meperidine, tramadol

    • Antiparkinsonian: amantadine, benztropine, ethopropazine, procyclidine, trihexyphenidyl

  • Cholinesterase inhibitors (for dementia): donepezil, galantamine, rivastigmine, memantine

  • Antipsychotics, neuroleptics (quetiapine, chlorpromazine, methotrimeprazine, risperidone, clozapine, olanzapine, fluphenthixol, loxapine)

  • Stimulants (used for ADHD): methylphenidate, amphetamine, dextroamphetamine, lisdexamfetamine

  • Antidepressants (particularly tricyclic antidepressants and SSRIs): citalopram, escitalopram, fluoxetine, fluvoxamine, paroxetine, sertraline, venlafaxine, desvenlafaxine, duloxetine, amitriptyline, clomipramine, nortriptyline

  • Lithium

  • Antiepileptics: carbamazepine, oxcarbazepine, clobazam, clonazepam, divalproex, valproic acid, gabapentin, pregabalin, lamotrigine, lacosamide, levetiracetam, phenobarbital, phenytoin, fosphenytoin, primidone, topiramate

  • Antiparkinsonian medications: amantadine, benztropine, ethopropazine, procyclidine, trihexyphenidyl

  • Thyroid medications: levothyroxine, liothyronine, dessicated thyroid

  • ACE inhibitors and ACE receptor blockers: benazeptil, catopril, enalapril, fosinopril, lisinopril, perindopril, quinaptil, ramipril, candesartan, irbesartan, losartan, telmisartan, valsartan

  • Vasodilators (e.g. nitrates and calcium channel blockers): amlodipine, felodipine, nifedipine, diltiazem, verapamil, nitroglycerine, isosorbine dinitrate, isosorbine mononitrate

  • NSAIDs: aspirin, indomethacin, diclofenac, ketorolac, ibuprofen, naproxen, meloxican, mefenamic acid, celecoxib

  • Certain antibiotics (sulfonamides: sulfamethoxazole, sulfasalazine) and antiretrovirals (indanavir)

Know how to keep yourself and others safe during a heat wave

Extremely hot weather can be dangerous for anyone, but especially for people who have multiple factors that put them at higher risk. Being well-prepared, including having a heat safety plan, can help keep you and those you care for safe.

Start with a Spring To-Do List

There are a number of things you can do in advance, so you’re not caught unprepared when a heat wave arrives. It’s like getting your winter tires on before the first snow fall.

Below is a Spring To-Do List that you can print along with a personalized Heat Safety Plan (discussed in more detail the next section). Print and use these to get your home, yourself, and those you care for prepared for summer heat waves. If you don’t have a printer, ask a friend, family member or someone else with a printer to print them for you. If you have a printer and know someone else who could also use the To-Do List and Heat Safety Plan, please consider also printing it for them.

Create a support group of one or more Check-in Companions

It’s a great idea to have a support network of nearby “Check-in Companions” (e.g. friends, family, neighbours) that you can stay in touch with and/or visit during heat waves or other emergencies. This is especially important if you know someone who is at higher risk during heat events (an older adult, someone who has chronic health conditions, or who lives alone), or if you yourself are at higher risk.

  • Find out who can be your Check-in Companion(s)—people you can stay in touch with and/or visit during a heat wave to make sure you’re both okay. If it helps, let them know your doctor recommended it. Write their name and phone number in the “Key Information” section of your Heat Safety Plan.

If you don’t have air conditioning (AC)

If you don’t have AC, or if your AC stops working, it’s important to know where you can go to cool down during a heat wave. Spending some time in air-conditioned spaces during extreme heat events is associated with a reduced risk of death. You should be able to stay in the air-conditioned environment until you feel cool and refreshed – generally at least an hour or two a day.

  • In the “Where I Can Go to Cool Off” section of your Heat Safety Plan, write down which of these are available to you if you need to cool down:
    • Nearby Check-in Companion or other person with AC
    • Room in your building that has AC
    • Library
    • Mall
    • Municipal shelter or facility
    • Recreation centre
    • Cinema
    • Pool, splash pad or beach
    • Place of worship with AC
    • Other place with AC: ____________________________
  • If you don’t know where you can go to cool down during an extreme heat event, you can call 211 for help and information. 211 is a 24-hour helpline that can connect you to local social services, programs and community supports.
  • It is also important to have plan for where you can stay overnight if your home gets too hot. Ask a friend, family member, or neighbour with air conditioning if you could stay with them in the event that your home becomes too hot, and write their name and phone number in the “Where I Can Spend the Night If My Home Becomes Too Hot” section of your Heat Safety Plan.

If you don’t have a car

  • In your Heat Safety Plan, enter the name of a nearby Check-in Companion or other person who can be available to drive you to a cool place or to the hospital if needed during a heat wave.
  • You may want to discuss transportation options with a family member. You can also call 211 or call your municipality to find out what local transportation options are available during a heat wave. Enter the contact information for requesting transportation in your Heat Safety Plan.

If you take medication

If you have mobility concerns

  • Make arrangements for someone to be available who can help you move to a cooler area of your home or help you with cool showers/baths during a heat wave. They should be able to visit you regularly and often.

Get your home ready

  • Identify the coolest area in your home. This could be a room with AC, or if you live in a house, your basement. The coolest area of your home is where you should spend most of your time during a heat wave. Plan how you can arrange the area so that you can take care of your daily activities there. If possible, arrange it so that you can also sleep in this cooler space.
  • If you have an air conditioner (AC), check to make sure it is in working condition.
  • If you have a fan, make sure it’s easily accessible so you can pull it out when needed.
  • If you don’t have an AC or fans, consider getting one or both. If cost is an issue, see: Financial assistance for air conditioning (AC) systems, fans and electricity costs. You can also call 211 to see if there is a local agency that can help you with the expense.
  • Make sure you have window coverings that you can use to block out the sun when it’s very hot outside. These can be blinds, curtains, shutters, or even a blanket or cardboard that you can put over windows when needed.
  • If you don’t have an indoor thermometer, arrange to get one (available at most hardware stores).
  • Keep a flashlight in an easily accessible place in your home.

Get personal supplies

  • If you don’t already have one, get an oral or ear thermometer so you can monitor your temperature, as well as your spouse’s, children’s or roommate’s temperature.
  • Make sure you have some light, loose-fitting clothing you can wear when it is very hot.
  • Get a spray bottle so you can mist water onto yourself when it’s very hot. As the water evaporates from your skin, it can help cool you down.
  • Make sure you have a water bottle that you can take with you if you have to go outdoors during a heat wave.

If you fast for religious reasons

  • Ask your religious leader if accommodations can be made to stay hydrated on days when there is a heat event.

Drinking water

  • If you don’t drink tap water, make sure you are always well stocked with bottled water.

Be prepared for power outages

  • Have a plan for potential power outages. Follow the tips at www.getprepared.ca.
  • Keep extra water on hand in case you need it during a power outage.
  • Make arrangements so that you can visit a Check-in Companion or other place with AC to cool off if your home becomes too hot – See “Where I Can Go to Cool Off” and “Where I Can Spend the Night If My Home Becomes Too Hot” in your Heat Safety Plan.
  • If you don’t already have one, consider getting a portable charger, power bank, or a solar recharger for your cell phone.

Monitor the weather

Get your body ready to handle summer heat

There are also things you can do early in the season to start getting your body ready to handle the summer heat.

  • Help your body adapt to heat by gradually increasing the amount of walking or exercising you do outdoors as the temperature warms up. This is best to do in the springtime.
  • Best results come when you stay hydrated and then take some time after to rest, hydrate and cool down.
  • When the summer arrives, be active during times of the day when heat is not at its peak (morning, late afternoons and evenings) with protection such as sunscreen, a hat, and light-coloured clothing that allows the body to sweat.
  • As your body gets used to warmer weather, sweating starts earlier, which starts to cool the body more quickly.
  • Pushing yourself to the point of heat exhaustion will not help your body adapt – in fact, it will make you more vulnerable to heat.
  • Eating regular meals will help your body adapt as food replaces electrolytes lost in sweat.
  • You need to continue spending time in heat to remain adapted to it. You begin to lose your acclimatization after about one week of not getting any exercise in the heat and after a few weeks, you will return to your baseline.

Creating a Heat Safety Plan can help you know what to do during a heat wave to reduce your risk and the risk of those you care for. Click here to print your Heat Safety Plan and keep it close at hand so you can find it easily when needed.

What to do when a HEAT WARNING is issued

Heat warnings are usually issued a day or two before a heat event begins. This gives you an important window of time to get yourself (or those you care for) ready.

  • Reach out to your Check-in Companions group. Make plans to stay in touch daily during the heat wave, and arrange for someone (your check-in companion, personal service worker, or someone else) to visit you regularly in case you need help. If you know someone else who needs help, make plans to visit them if possible.

  • Monitor the weather on your WeatherCAN app or online at www.weather.gc.ca

  • Renew your meds, get groceries, and get personal and pet supplies, if needed.

  • If you don’t drink tap water, make sure you’re well stocked with bottled water.

  • If you have a car, make sure it has a full tank of gas or is fully charged.

  • Follow your pharmacist’s advice regarding any medications that may increase your risk during a heat wave.

  • If you fast, make sure you stay hydrated. It is not safe to restrict your water intake during a heat wave.

  • Make sure any supplies you might need (fan, flashlight, batteries, indoor and body thermometers, etc.) are close at hand.

  • Consider closing your blinds or curtains ahead of the heat wave, to block sunlight and help prevent your home from heating up as quickly. A low-cost option is covering windows with cardboard or blankets.

  • Be prepared to leave your home to go to a cooler place if it gets too hot. See “Where I Can Go to Cool Off” and “Where I Can Spend the Night If My Home Becomes Too Hot” in the Key Information section of your Heat Safety Plan.

  • To learn more about how to keep children safe during extreme heat, see this resource from Health Canada: Keep children cool! Protect your child from extreme heat.

What to do DURING the HEAT EVENT

  • Call your Check-In Companion(s) at a pre-planned time each day to check on each other throughout the heat wave. If you’re able to check-in in person, even better.

  • Monitor the weather on your WeatherCAN app or online at www.weather.gc.ca

  • If you have an air conditioner, turn it on! It plays an important role in protecting you from heat-related illnesses.

  • Avoid spending time outdoors from 10 AM to 4 PM. If you do go out, wear light clothing and a hat, bring a water bottle, and take frequent sips.

  • Close your blinds or curtains during the day or block your windows with cardboard or blankets.

  • If there is a power outage, follow your emergency plan or use the tips at getprepared.ca. Be prepared to leave your home if it gets too hot.

If your home is warm/hot:

  • Use fans to keep air moving and to help you feel cooler (only if the room temperature is below 35°C or 95°F).

  • Take off extra layers of clothing to expose as much skin as possible so that it can cool down more easily.

  • Limit caffeine/alcohol to avoid dehydration.

  • Avoid using your oven. Use the microwave to heat things or make food that doesn’t require cooking (like sandwiches, cold soups etc.).

  • Turn off non-essential devices that generate heat.

  • Fill a spray bottle with cool water and spray it on your face and neck – it will help you cool down as the water evaporates off your skin.

  • Keep wet towels in a plastic bag in the fridge and place them on your neck, chest or back when hot.

  • Spend time in an air-conditioned environment until you feel cool and refreshed – generally at least an hour or two a day.

    • See “Where I Can Go to Cool Off” in the Key Information section of your Heat Safety Plan.

    • If you don’t know where you can go to cool down, call your municipality to see if they have opened a cooling shelter. You can also call 211 for assistance. 211 is a 24-hour helpline that can connect you to local social services, transportation options and community supports.

    • If you live in the Ottawa area, a map of places to cool off in Ottawa is available here.

  • Spend time in cool water (take cool showers/baths, sit with your feet in a pail of cool water, or visit a pool).

  • Make sure you’re drinking enough water. Drink often and before you feel thirsty to replace fluids. When you’re dehydrated, it’s hard on the heart. Certain chronic conditions can start to get worse, or heat exhaustion can set in.

    • If you’re passing urine that’s darker than usual or you haven’t peed for many hours, you may be dehydrated. Drink more water.

  • Open your windows if the temperature outside is cooler than inside, there is no air quality warning in your area, and if it safe to do so.

  • Sleep in a cool room, if possible (if you live in a house, the basement is often the coolest place to sleep). Being able to stay cool overnight can make a big difference in your ability to tolerate the heat.

  • Monitor your indoor temperature: Aim to keep your indoor temperature no higher than 26°C (78.8°F). If your indoor temperature increases and remains higher than 26°C, you may need to leave your home to stay in a cooler space.

    • See “Where I Can Go to Cool Off” and “Where I Can Spend the Night If My Home Becomes Too Hot” in the Key Information section of your Heat Safety Plan.

Monitor how you and others are doing

  • Take your body temperature daily during the heat wave and if you start feeling hot, take it every hour or two. If you have children or others in your care, do the same for them.

    • Normal body temperature is 37oC (98.6 oF) although it can range from 36.1-37.2°C (97-99°F)

  • If your body temperature goes above 37.2°C (99°F) this may be a sign that your body is having a hard time releasing its excess heat. Try some of the cooling techniques above and take your temperature again.

    • If your temperature returns to normal, that’s a good sign.

    • If your temperature stays the same, try adding a new cooling strategy (e.g. sitting with your feet in a pail of cool water).

    • If your temperature is greater than 37.2°C (99°F) and doesn’t respond to cooling: Go to a cooler or air-conditioned space to cool down. See “Where I Can Go to Cool Off” and “Where I Can Spend the Night If My Home Becomes Too Hot” in the Key Information section of your Heat Safety Plan.

    • If your resting body temperature rises above 39°C (102.2°F), you are in the DANGER ZONE – Call 911.

  • If at any time you start feeling unwell or have increased symptoms from any of your chronic conditions, even after taking measures to cool yourself (or if your symptoms return after cooling measures stop): Go to a cooler or air-conditioned space to cool down. See “Where I Can Go to Cool Off” and “Where I Can Spend the Night If My Home Becomes Too Hot” in the Key Information section of your Heat Safety Plan.

    • If you continue to feel unwell, get help. Call Health811 at 811, or if your symptoms worsen, call 911.

The danger zone is when you are in a situation that has the potential to escalate into a crisis. If you or someone else enters the danger zone, it is important to take immediate action.

If your home becomes very hot, follow the measures in your Heat Safety Plan to cool yourself down and be ready to leave your home to go to a cooler space if needed.

Becoming overheated can quickly become dangerous. If you experience any of the symptoms below, you are in the danger zone. Do not go to sleep when you are in the danger zone.

  • HEAT EXHAUSTION: Weakness, headache, nausea/vomiting/diarrhea, thirst, dark urine, intense fatigue. If you experience any of these symptoms during extreme heat, immediately move to a cool place and drink liquids. If symptoms are not relieved by drinking water, resting and cooling, call 911.

  • HEAT STROKE: Red and hot skin, dizziness, nausea, confusion, loss of coordination or a change in consciousness. Heat stroke is a medical emergency! Call 911.

  • If your resting body temperature rises above 39°C (102.2°F), you require immediate emergency attention: Call 911.

If you are waiting for medical attention for someone else, try to cool the person by moving them to a cool place, removing extra clothing, and applying cold water or ice packs around their body.

Evidence has shown that social isolation is an important risk factor for a heat-related illness.

If you can, check on the people you know. It can be as simple as a phone call, a text, a short visit, or an invitation to come over to your place (especially if you have air conditioning).

If you are worried about someone, here is a useful checklist you can use to see if they are safe or not and what to do: Health Checks During Extreme Heat Events

What if someone you know should leave their home, but they refuse?

It is always a tough situation when you’re worried about someone and want them to get to a safe air-conditioned place, but they don’t want to go.

Here are a few options to consider:

  1. Try to understand why they are saying no. It may be that they:

    • Are worried about leaving their pet – usually a solution can be found to address this.

    • May not feel they would be welcomed at a cooling centre.

    • May underestimate their risk or be in denial about the seriousness of their health condition.

  1. Try to reframe it in a way that emphasizes a benefit that is important to them.

  2. Suggest that you call Health811 together and get an objective opinion. Simply dial 811.

  3. Respectfully agree and then tell them you will check on them again in 30 to 60 minutes to reassess their situation.

    • If you find that their symptoms are getting worse, or they have become confused or lost coordination, you need to call 911. Encourage them to lie down, drink cool water and start cooling measures (such as putting a cool, wet towel on their neck or head) as you wait for the ambulance.

  1. In very tough situations, you may have to stand down but decide to call the police and request a “Safety Check”. This can be useful, especially if the police have a policy to visit with a social worker.

Some people assume that pets are healthy and can handle the heat, but they can be vulnerable too. Make sure your pets have plenty of water and, if outside, are in the shade as much as possible.

Have a plan for what you will do with your pets if you need to leave your home to go to a cooler space.

  • If you’re going outdoors during a heat wave, monitor the weather and Humidex and adjust your plans accordingly. Keep in mind that the risk of a heat-related illness starts to rise when the Humidex is 35-39 (and can start in low 30s if someone has multiple risk factors).

  • Plan your activities so you minimize exposure to extreme heat. Avoid going out during the hottest hours of the day. Consider doing physical activities indoors where there is air conditioning.

  • Have the following when you go out:

    • Light, loose-fitting clothing, so your body can release any accumulated heat

    • A hat or umbrella to protect you from direct sun and sunburn

    • A water bottle to keep you hydrated

    • Sunscreen and if needed, insect repellent

  • Make sure you drink enough water to stay well hydrated. Drink a glass of water before going outdoors, and take frequent, small sips of water when outside.

  • Know the four ways heat can be released from the skin.

Staying safe if you do prolonged or strenuous outdoor activities (like preparing for a marathon or competing in a beach volleyball tournament)

Some athletes and other fit people assume they are fit enough to be resilient against heat – not always. To stay safe:

  • Consider rescheduling strenuous outdoor activity to a cooler part of the day or another day, or find alternative ways to work out – for example, exercise in an air-conditioned place, or choose a cooler outdoor location such as a tree-shaded area away from high traffic to avoid higher levels of air pollution. These spots can be as much as 5°C/9°F cooler than the surrounding area.

  • Check the Air Quality Health Index (AQHI) before you head out for strenuous activity, such as a multi-kilometre run. Air pollution tends to be higher during extreme heat. When active, you’re more sensitive to air pollution because you breathe deeply and allow more air to enter your lungs.

  • Avoid sun exposure – sunburned skin loses its sweating efficiency, which reduces your body’s ability to maintain a normal temperature. Shade yourself by wearing a wide-brimmed, breathable hat. Use a sunscreen that is SPF 15 or higher and follow the manufacturer’s directions. Remember, sunscreen will protect you from the sun’s ultraviolet (UV) rays but not from the heat.

  • If you’re in an area where mosquitoes are active, protect yourself with insect repellent. If it’s sunny, use sunscreen first and then insect repellent.

  • Take extra water breaks – you may not notice you’re getting dehydrated. Look for shade, drink water and remove gear, such as a helmet or equipment, and let your body cool off.

  • Don’t expect the usual performance from yourself during extreme heat. Exercise puts an added load on the heart as it directs blood to the muscles. In heat, there are additional signals to send blood to the skin so that heat can be released from the body through sweat and evaporation. If you exercise in the heat it puts a double load on the heart. This can lead to:

    • Muscle cramps – can happen suddenly, often in the calves. Stop and see if you can massage them out. Consider some electrolytes in your water.

    • Heat fainting (syncope) – people can faint if they become too overheated, but they should not faint for more than one minute. If they don’t wake up, call 911.

    • Heat exhaustion can also occur.

  • If your running partner – or anyone you see while you are outside – becomes confused and loses coordination, call 911 as this is a medical emergency. They may be developing heat stroke and could go unconscious.

    • While waiting for help – get the person to a cool place right away, pour water from a water bottle onto the skin or clothing; and fan the person as much as possible to help them cool down.

  • If at any time you start to have any symptoms of a heat-related illness (faint-headedness, weakness, headache, nausea, vomiting or diarrhea, or you feel like one of your chronic conditions are getting worse), drink cold water, pour cold water on some of your clothes to cool you down, and get to an air-conditioned place as soon as possible (even a store to get more cold drinks). If your symptoms get worse before you can get to air conditioning, call 911.

  • Allow your body to recover after heat exposure. Go for a gentle swim in a pool to cool down, spend an hour or so in a tree-shaded area or somewhere that’s air conditioned, and take frequent sips of water.

  • Try to spend as much time as possible in a cool environment. This could be at the home of someone you know who has air conditioning, a local library, mall, municipal shelter or facility, recreation centre, pool, or a place of worship. You can also cool down by spending time in cool water at a pool or splash pad.

  • If you don’t know where you can go to cool down, ask around or call 211 for assistance. 211 is a 24-hour helpline that can connect you to local social services, shelters, free water distribution spots, transportation options and other community supports.

  • If you live in the Ottawa area, a map of places to cool off in Ottawa is available here.

  • When outdoors, try to stay in the shade. If you are living in your car, try to park it in the shade, and if safe, roll down the windows.

  • Try to drink plenty of water, and follow the outdoor safety measures described in Protect yourself outdoors.

  • If you can, fill a spray bottle with cool water and spray it on your face and neck – it will help you cool down as it evaporates off your skin.

  • Eating helps to keep your electrolytes normal. If funds are tight, go to a food bank when it’s not too hot to get water-rich foods, like soups, fruits and vegetables. Call 211 to find out where your local food banks are and how to get there.

  • If you start to enter the “Danger Zone”, get help immediately.

  • Never leave children or pets in a parked vehicle! Even with the windows cracked open, an outdoor temperature as low as 23°C (73°F) can quickly rise to 50°C (122°F) or more in a parked car.

  • Don’t leave your medications in a parked car, as the heat can cause them to degrade or explode.

Below is an overview of available programs in Eastern Ontario (as of March 2025) for eligible individuals.

Municipal programs:

  • Coolsaver Rebate Program (Ottawa): In collaboration with Hydro Ottawa and Hydro One, the Coolsaver Rebate Program offers Ottawa homeowners free tune-ups for existing central air conditioners or central heat pumps, valued up to $250.
  • Better Homes Ottawa (Ottawa): Low-interest loans from the City of Ottawa to cover the cost of home energy efficiency improvements (for example, heat pump installation).
  • Low-Income Energy Assistance Program (LEAP) Emergency Financial Assistance Program (Cornwall): Provides one-time emergency financial assistance for residents facing financial hardship and struggling with electricity bills.
    • Eligible customers can receive grants credited directly toward their energy bills. To apply, contact the United Way of Stormont, Dundas & Glengarry at 1-855-487-5327 or visit their office at 55 Water St W, Suite 240, Cornwall, ON.

Provincial programs:

  • Home Renovation Savings Program: Offers rebates of up to 30% for home energy efficiency renovations and improvements, including new windows, doors, insulation, air sealing, smart thermostats, and heat pumps.

  • AC subsidy for people on social assistance (OW/ODSP): Cooling devices, such as air conditioners, can be obtained with a prescription from a nurse practitioner or physician. A diagnosis is required, and it must indicate that a cooling device is required as a part of a treatment plan. It is important that the prescription indicates that failure to obtain this device would result in a hospitalization or a severe risk to life.

    • Cancer
    • Chronic heart or chronic lung conditions such as Chronic Obstructive Pulmonary Disease (COPD)
    • Neurological conditions
    • HIV
    • People on dialysis
    • People with chronic mental disorders on medication
    • Severe asthma

Federal programs:

After the heat wave is over

All heat waves come to end. When all has settled down, it is useful to go over in your mind — and discuss with others — how things went.

Consider:

  • What went well? It’s important to celebrate successes. You worked hard to be ready for this heat wave – we hope you felt like it paid off!
  • What didn’t work as well and why? Was there anything you felt unprepared for?

No plan is perfect and there are often unforeseen issues. What could make your plan and actions better?

  • What additional actions or things might have helped? In general, any plan can be improved in retrospect. Take advantage of the clarity that comes from living through an extreme heat event, to think about what else could have been done.

Review and revise your Heat Safety Plan

Heat waves aren’t going away. They will undoubtedly be back next summer. Capture what you have learned this summer so you can improve your plan for next year.

Share your feedback

Don’t hesitate to give us suggestions or feedback. If you think there is something that could be useful to add to this document, please let us know at: info@cpin-rcip.com