Extreme Heat




How does heat affect our health?

In the summer, the sun and beautiful weather are great sources of enjoyment… However, when the heat is too extreme, it is stressful to the body. Several organs, including the heart, have to work harder to resist the heat.

The effects of heat on health are more serious: 

  • During the first heat waves, since the body is not used to high temperatures
  • If the heat lasts for several days, or nights stay hot
  • When it is very humid and there is no wind
  • If you live downtown, where the heat is more intense
  • If you do not have air-conditioning in your home

Indirect effects

The most common effects of heat on health are indirect. They are associated with worsening of symptoms in people who are already sick.

Direct effects

Although quite rare, the direct effects of heat are cramps, heat exhaustion and heatstroke. These effects can occur among people who are already sick or among healthy people who do strenuous physical activity in spite of the heat.

In case of heat stroke (elevated body temperature, confusion), emergency medical treatment is required. For heat cramps or heat exhaustion, rest in a cool place and drink water or a water-diluted sports beverage. If symptoms worsen or last more than an hour, consult a doctor.


What to do in Case of Heat Warning or Extreme Heat

When it's very hot, your health can deteriorate rapidly. To protect yourself from the effects of heat:

  • drink 6 to 8 glasses of water a day or as directed by the doctor;
  • spend at least 2 hours a day in an air-conditioned or cool place (shopping center, library, etc.);
  • take at least 1 shower or 1 fresh bath a day or refresh your skin several times a day with a wet towel;
  • avoid alcohol reduce physical effort wear light clothing
  • get news of your loved ones, especially those who are losing their autonomy or who live alone.

If you feel unwell or have any questions about your health, call Info-Santé 811 or ask a health professional.

In case of emergency, call 9-1-1.


Additional preventive measures for people who are at higher risk

People at risk Preventive measures

Elderly people suffering from chronic cardiovascular, cerebrovascular, respiratory, kidney, or neurological diseases or diabetes

People taking medications such as tranquilisers, diuretics or anti-cholinergics

CAUTION! People at risk who live alone are twice as vulnerable during extreme heat waves.

1. To better prepare yourself for heat waves:

  • Stock up on water and sports beverages
  • Find a cool place to rest, in case the need arises.
  • Identify someone who can be contacted daily, in case there is a problem
  • Keep the Info-Santé telephone number within easy reach 

2. During heat waves:

  • Be proactive by following basic preventive measures before you feel the effects of heat
  • During hot nights:
    • Find a cool place to sleep
    • If this is not possible:
      • Sleep with the windows open
      • Keep some water by the bed
      • Do not hesitate to have something to drink, or take a shower or bath during the night
      • To cool off, use a damp cloth
  • Pay attention to your state of health. In case of general malaise, dizziness, fatigue, head ache, difficulty breathing, chest pain or swollen legs, contact Info-Santé or your doctor.
  • Discuss with your doctor any changes that might be required to your medication or to your medical follow-up. This is especially important for people with the following medical problems:
    • Heart failure
    • Patients on dialysis
    • Loss of fluids due to gastrointestinal problems
  Young children (0 to 4 years of age)

Parents should make sure that their children:

  • Drink plenty of fluids
  • Take cool baths more often
  • Wear lightweight clothing
  • Are never left alone in a car
People who take part in strenuous activity (jogging, bicycling, etc.)
  • Reduce the intensity of activity
  • Practice the activity earlier in the morning
  • Drink sports beverage diluted with water
Construction workers (or other outdoor manual labour) or people who work in places where heat is emitted through industrial processes (foundries, bakeries, dry cleaners, etc.) Get a copy of the pamphlet “Attention au coup de chaleur” available in French in all CNESST regional offices

Keep an eye on others!

During heat waves, we need to pay special attention to those around us who are most at risk. The following people may be unable to take protective measures without someone’s help, especially if they live alone:

  • People with mental disorders
  • Disabled people
  • Elderly people with chronic diseases
  • People who take tranquillisers, diuretics or anti-cholinergics

Whether somebody is a neighbour, a relative or a friend, do not hesitate to call or knock on the door of anyone around you who is at risk and offer them a hand.


Useful Emergency Numbers

Emergency : 9-1-1

Info-Santé : 8-1-1

CIUSSS de l'Ouest-de-l'Île-de-Montréal : 514 697-4110