Santé Montréal

WHAT ARE EXTREME HEAT AND HEAT WAVES?

Extreme heat

The temperature reaches 30 °C and the Humidex value (combination of relative humidity and temperature) reaches 40 °C. An extreme heat event causes discomfort.

Heat wave

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.

In either case, heat can have serious health effects. Vulnerable people can have health problems caused by heat exhaustion.

Symptoms

The main health problems caused by heat exhaustion are :

  • dehydration (dry mouth),
  • headaches,
  • dizziness,
  • confusion,
  • fainting.

WHAT TO DO DURING EXTREME HEAT EVENTS AND HEAT WAVES

Advice for everyone: When it's really hot, do the following:

  • Spend a few hours a day in a cool, preferably air-conditioned place.
  • Drink a lot of water, even before you feel thirsty.
  • Reduce physical effort.

Advice for seniors and other vulnerable people:

  • Follow the same advice as for the general population.
  • Family members and friends should check in on them regularly to make sure they are following the recommended preventive measures, and to give them any help they may need. 
  • For more information, see It's very hot! and prevention messages in various languages.
  • People with mental health problems can get more information by viewing the Heat and Mental Health information sheet.

Advice for children aged 0 to 4

  • See the It's really hot! information sheet  (French version: Il fait chaud).
  • Documents for parents and caregivers of children aged 0 to 4 is available here in various languages.

When to get help 

If you develop these symptoms, call Info-Santé at 8-1-1 or talk to a health professional. 

If there is fever in addition to those symptoms, heatstroke could occur, which is a medical emergency. In this case, call 9-1-1 for help.

Notice

Health monitoring data

Cumulative dataNumberUpdated on
Reports of deaths probably linked to the heat wave in Montréal348 July 2018, at 11 AM


These indicators are from daily health monitoring carried out by Direction régionale de santé publique de Montréal (CIUSSS du Centre-Sud-de-l'Île-de-Montréal).