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 around 31 and 33 ºC daytime, and between 16 and 20 ºC at night for 3 consecutive days.


For adults

During heat waves, your health may deteriorate rapidly. Certain precautions must be taken to make yourself more comfortable and reduce health risks for you and your loved ones.

  • Keep well hydrated
    • Drink 6 to 8 glasses of water a day. If necessary, follow your doctor’s instructions for the amount of liquid to drink
  • Avoid alcoholic beverages as alcohol can exacerbate dehydration
  • Refresh yourself often:
    • Bathe, shower or take a cool bath daily
    • Refresh your skin with a wet towel several times a day
    • Spend at least 2 hours a day in cool and air-conditioned places (libraries, shopping centers, etc.)
  • Protect yourself from heat:
    • Limit physical effort
    • Wear light clothing
  • See how your loved ones are doing, especially those with reduced autonomy or that live alone
  • Watch for heat notices and heat alerts, and follow the recommendations of Environment Canada or your region’s public health authority

For babies and children

During heat waves, the health of babies and children can deteriorate fast. Certain precautions must be taken to make them more comfortable and reduce health risks.

  • Hydrate your children well:
    • Give them a glass of water every 20 minutes
    • Breastfeed your baby more often
    • Offer water between feedings to bottle-fed babies
  • Refresh them often:
    • In a pool or by making them take a cool bath or shower at least twice a day
    • Refresh 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 competitive endurance sports
    • Plan outdoor activities before 10 a.m. and after 3 p.m. when the heat is less intense
    • Limit or stop physical activities for children with an acute or chronic illness