Extreme heat

When temperatures hit 32°C or more, for three or more days, it’s considered a heat wave or conditions of extreme heat. Poor air quality can cause additional health concerns when extreme heat combines with air pollutants from industry, gas-powered vehicles, and other sources.

When extremely hot temperatures are forecast, the City offers residents places to stay cool in Mississauga. These include visiting one of our swimming poolsair-conditioned libraries, spray pads and community centres.

When a heat warning has been issued by the City, residents are encouraged to call before visiting one of these locations as hours of operation vary.

For more information on extreme heat alerts and how to stay cool, please visit the Peel Region.


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 are in direct sunlight with drapes or shades
  • Stay indoors if you can
  • Drink plenty of water, even if you are not thirsty
  • Dress in loose, light-coloured, lightweight clothing and 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