A heat wave is defined as three or more days of temperatures of 32°C or more. In the summer,
there is added threat of poor air quality when extreme heat combines with air pollutants from
industry, gas-powered vehicles, and other sources.
Environment Canada can issue a humidex:
The humidex values represent the effect which high humidity and high temperatures have on
the human body. Under normal conditions, the body's internal thermostat produces perspiration
that evaporates and cools the body. Under extreme heat, evaporation is slowed the body must
work harder to maintain normal core temperature. A humidex advisory is issued when temperatures
are expected to reach 30°C or more, and when humidex values are expected to reach 40 or more.
The higher the humidex, the harder it is for perspiration to evaporate and cool the body.
Ministry of the Environment can issue Smog Alerts:
Smog levels indicate and forecast the current air quality information. Most smog days in
Ontario occur between May and September. When it is issued, avoid or reduce strenuous physical
outdoor activities, avoid exercising near areas of heavy traffic, and if you have a heart or
lung condition, inquire with your physician on how to protect your health .
How to prepare:
- 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
- Stay indoors if you can.
- Eat well balanced meals
- Drink plenty of water, even if you are not thirsty.
- Limit alcohol and caffeine.
- Dress in loose, light-coloured, and lightweight clothing; cover as much skin as
- Public buildings like libraries, movie theatres, shopping malls, and community facilities