Extreme heat

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

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

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

Prepare an emergency kit.

Stay informed of weather alerts  in effect in your region. Take those alerts into consideration when planning activities.

Find out about the recommended safety precautions to prevent heatstroke  (French only) in the workplace.

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. 
• Avoid alcoholic beverages, because alcohol can make dehydration worse.
• Cool off often:
  • take a cool shower, a bath or take a dip in a swimming pool, if possible;
  • Place a cool wet towel on your face, arms and neck, and spray cold water over your face several times a day;
  • spend a few hours a day in an air-conditioned place or a cooler place in your home.
• Protect yourself from heat:
  • reduce physical exertion;
  • wear lightweight, light-coloured and loose-fitting clothing. Wear a wide-brimmed breathable hat;
  • schedule your physical activities during the cooler parts of the day (such as before 11 a.m. and after 6 p.m.).
• Close the curtains or blinds when the sun is out. If possible, air your home at night when it is cool.
• Minimize your use of heat-producing appliances (stove, oven, clothes dryer, television, light fixtures, etc.).
• Stay in touch with your loved ones and do not hesitate to ask family and friends for help during periods of high heat:
  • The most vulnerable people should regularly invite people over to visit (family, neighbours, friends).
  • The loved ones of people who are elderly, frail or living alone should visit them regularly.
• Watch for heat warnings and follow the recommendations of Environment Canada or your region’s public health authority.

If your condition or that of a loved one worsens, or if you or a loved one is vulnerable to the heat, contact Info-Santé 811 for medical advice. In a medical emergency, call 911 or go to the nearest hospital.

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;
  • wet 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, even if the windows are cracked open.
• 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.

Find out from your municipality what measures have been implemented to ease the consequences of a period of extreme heat, such as the opening or extension of opening hours of certain municipal services (ex.: pools, water play areas, premises with air conditioning, etc.).

Pay close attention to your pets, as they can suffer from the heat  (French only) as well. Do not leave them exposed to the sun and give them water to keep them hydrated. Never leave a pet alone in a car, even for a few minutes.

Respect the restrictions regarding access to wooded areas, as well as vehicle traffic, work and outdoor fires during a heat wave. Beware of vegetation that has dried out, including in your garden. Comply with restrictions on open-air fires and be informed on the precautions to take and the safety rules to follow in the event of a forest fire.

During a drought, watering restrictions may be issued by municipalities to ensure the supply of drinking water for the entire population.