Heat and extreme heat
Environment Canada issues "heat alerts” when the temperature reaches 30 °C and the humidex (temperature and humidity combined into one number to reflect the perceived temperature) reaches 40. The main effect of heat on the population is discomfort.
The term "extreme heat" has been defined by public health authorities to plan for heat events as a means of foreseeing heat episodes that are likely to have an impact on the health of vulnerable individuals. In Montréal, an "extreme heat" episode is defined as three consecutive days when the average maximum temperature reaches 33 °C and the average minimum temperature does not drop below 20 °C, or when the temperature does not drop below 25 °C for two consecutive nights. Environment Canada does not issue extreme heat alerts, but its weather forecasts are used to anticipate situations which could cause health problems.
- When it's very hot, some people are at greater risk of developing heat-related health problems. Older people, young children, people with heart or lung disease, and people with mental health problems or drug or alcohol problems can be affected more than the rest of the population.
- There have been at least five extreme heat episodes in the Montréal region since the 1980s.
- The main health problems linked to heat are the following: dehydration, headaches, dizziness, confusion, fainting.
- If these symptoms are present, call Info-Santé at 8-1-1 or talk to a health professional.
- If you have fever in addition to these symptoms, you may have heatstroke, which is an medical emergency. In this case, call 9-1-1 to get help.
When to Consult
Protection and prevention
What can you do to prevent problems and protect yourself?
When it is very hot, you need to:
- spend a few hours a day in a cool and preferably air-conditioned place;
- drink a lot of water, without waiting to be thirsty; and
- reduce your level of physical exertion.
The families and friends of elderly people and of people with chronic diseases or mental health problems or drug or alcohol problems should check in on them regularly during heat waves to make sure that they are taking the recommended preventive measures and to give them any help they may need.
People at risk and their families or friends can learn what they should do during periods of heat or extreme heat, by reading the "It's really hot!; PDF 450 KB (available in French under the title; Il fait très chaud!)
Information on heat episodes is also available in other languages. Click on the language of your choice to download the documents:
Preventive measures in various languages:
People with mental health problems
People with mental health problems can also follow protect themselves against the heat by following the advice given in the following information sheet: Heat and Mental Health.
Children in the 0 to 4 year-old group
Documents in various languages for parents and caregivers of children aged 0 to 4 years (140 KB PDF files):
Whom should you contact to get help?
Where can you find additional, credible information?
- The Effects of Oppressive and Extreme Heat
- Chaleur accablante page on the website of the Ministère de la Santé et des Services sociaux (website in french only)
- Travailler à la chaleur, attention! – information for workers on the website of the CSST (website in french only)
- Environment Canada's five-day forecasts
Information for Montréal region employers and employees, especially in the construction industry and municipal services
Any kind of work done in hot weather exposes workers to health risks, and the risks are greater during the first days of a heat wave. Our bodies take time to adjust to a rise in temperature, and all the more so if we have to perform demanding physical tasks, at a sustained pace in a place that is poorly ventilated or exposed to the sun. Preventive measures must be taken depending on the circumstances.
In addition to drinking a lot of water and covering yourself lightly to protect yourself from heatstroke, you can get useful tips from the CSST on heatstroke and how to prevent it (in French only), especially when you are working. You'll also learn how to recognize the first signs of heatstroke and what to do if a colleague or employee starts feeling ill.
Help and Resources
Whom should you contact to get help?
- In the event of a malaise, call a doctor or check with Info-Santé at 811.
- In case of an emergency, call 911.
People at Risk
Everyone should take precautions during heat or extreme heat episodes, but some people are more at risk than others, namely:
- elderly people
- people suffering from chronic diseases such as diabetes or cardiovascular, respiratory, renal or neurological diseases and people with mental health problems or drug or alcohol problems
- 0- to 4-year-old children.
Dernière mise à jour le : 2015.05.22