In Canada, heat warnings are issued by Environment Canada when the following conditions are expected to last for at least one hour:

  • a temperature of 30 ° C or higher and a humidex of 40 or more;
  • or a temperature of 40 ° C or higher.

The definition of extreme heat varies by region. On average, the temperature must be between 31 and 33ºC in the daytime and between 16 and 20ºC at night for 3 consecutive days.

Extreme heat in the context of COVID-19

During periods of extreme heat, public health authorities usually recommend that people go to an air-conditioned place such as a shopping mall or municipal library to cool off. At this time, when many air-conditioned public places are closed, people are advised to spend a few hours a day in air-conditioned or cooler places in their home and to follow the measures indicated on this page.

If you go to an air-conditioned public place, you must maintain a physical distance of 2 metres and follow the health recommendations​​​​​​​.


For adults

During a heat wave, your health can deteriorate rapidly. You can take certain precautions to make yourself more comfortable and reduce the health risks for you and your loved ones.

  • Make sure you drink enough fluids:
    • drink a lot of water. Don’t wait until you feel thirsty. Follow your doctor’s instructions for the amount of liquid to drink, where applicable.
  • Avoid alcoholic beverages, as alcohol can make dehydration worse.
  • Cool off often:
    • take a cool shower or bath as often as necessary;
    • cool your skin with a wet towel several times a day;
    • spend a few hours a day in air-conditioned or cooler places in your home.
  • Protect yourself from heat:
    • reduce physical exertion;
    • wear light clothing.
  • Close the curtains or blinds when the sun is out. If possible, air your home at night when it is cool.
  • Stay in touch with your loved ones and do not hesitate to ask family and friends for help.
  • Watch for heat warnings and follow the recommendations of Environment Canada or your region’s public health authority.

For babies and children

In hot weather, babies’ and children’s health can deteriorate quickly. You can take certain precautions to make them more comfortable and reduce the health risks.

  • Make sure your children drink enough fluids:
    • Have them drink water regularly and, if possible, give them a water bottle
    • For breastfed babies, breastfeed on demand. It is completely normal for the baby to nurse more often
    • Offer formula-fed babies formula more often
    • Offer babies over six months of age small amounts of water after or between feeds
  • Cool off children often, for example:
    • have them take a lukewarm bath or shower as often as necessary;
    • cool their skin with a wet towel several times a day.
  • Protect them from the heat:
    • dress them in light clothing;
    • cover their head with a wide-brimmed hat;
    • never leave them alone in a poorly ventilated room;
    • never leave them alone in a car.
  • Limit their exposure to heat:
    • limit their outdoor activities, such as endurance sports competitions;
    • plan outdoor activities before 10 a.m. and after 4 p.m. when the heat is less intense;
    • limit or stop physical activities for children who have an acute or chronic illness.