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Heat Wave

Heat Waves

A heat wave is defined as three or more days of temperatures of 32°C or more. Poor air quality can pose additional health concerns when extreme heat combines with air pollutants from industry, gas-powered vehicles, and other sources.


Humidex values measure how hot the weather feels to the average person. Under normal conditions, your body produces sweat that evaporates to cool you down. Under extreme heat, the body must work harder to maintain its normal temperature. A humidex advisory is issued when humidex values are expected to reach 40 or more. The higher the humidex, the harder it is for your body to cool itself.

Smog Alerts

Smog levels indicate and forecast the current air quality information. Most smog days in Ontario occur between May and September. When an alert is issued, avoid strenuous physical outdoor activities. If you have a heart or lung condition, consult your family doctor on how to keep healthy in the heat.

How to prepare for a heat wave

  • Install window air conditioners, insulate if needed.
  • Check air conditioning ducts for proper insulation.
  • Install temporary reflectors (aluminium cardboard) to reflect heat back outside.
  • Weather-strip doors and windows to keep cool air inside.
  • Cover large windows that receive sun's heat with drapes or shades to reduce heat entering the home.
  • Stay indoors if you can.
  • Drink plenty of water, even if you are not thirsty.
  • Dress in loose, light-coloured, and lightweight clothing; cover as much skin as possible.
  • Use public buildings like libraries, movie theatres, shopping malls, and community facilities that are air-conditioned to cool down and take a break from the heat.

This guide outlines steps that you and your family can take right now to best ensure that you are prepared for flood emergency events in your community. View and Download.

Emergency Preparedness Tips