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Heat Safety Index & Air Quality Index

Heat Safety Index

The Heat Safety Index will help you make a decision about whether or not outdoor exercise is safe.

  1. Check your local weather conditions to find the current temperature and humidity reading.
  2. Look for the temperatu​re along the bottom of the graph.
  3. Look for the percentage of humidity along the left hand border of the graph.
  4. Find the place on the graph where these two points come together. The zone that you are in can tell you whether it is safe to exercise outdoors.
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To use this scale, look for the air temperature along the bottom of the scale and percentage of humidity along the left-hand border. The intersecting points will indentify one of four zones.

What to do for each heat safety zone

Safety zoneWhat to do
Safe Zone
  • Exercise as usual.
  • Safe to exercise outdoors.
Alert Zone
  • Decrease your exercise intensity (slow your walking pace).
  • Watch for signs (such as shortness of breath, increased tiredness).
Danger Zone
  • No outdoor exercise.
  • Exercise in an air conditioned environment only.
Emergency Zone
  • Avoid going outdoors.

Be Aware of Air Quality

Air pollution and smog are very serious health concerns. Anyone can be affected especially:

  • young children
  • the elderly
  • those living with heart or lung disease

S​​​mog

Smog can irritate the eyes, nose, and throat. It can also cause coughing, wheezing and chest tightness. Smog is highest in Canada on hot sunny days between noon and early evening, usually between May and September. Do not exercise outdoors during the late afternoon and early evening when smog is at its highest.

Environment Canada provides smog advisories to warn of high smog levels. See Environment Canada's smog advisories (opens in new window) »

There are two levels of smog alerts.

  • A smog watch is issued when there is at least a 50% probability that smog conditions will occur within the next three days.
  • A smog advisory is issued when there is a high probability of a smog day occurring within the next 24 hours.

Air​​​ pollution

Air pollution can be measured by the air quality index. This tells us the levels of common air pollutants. Depending on where you live, the readings could range from 0-10 or 0-100. The lower the number, the better the air quality.

Go to your local municipal or provincial public health website to find out how your area lists the Air Quality Index. For Ontario, the range is from 0-100.

Check the air quality index before you exercise outdoors. Follow the directions based on the results.

Air Pol​lution

Diagram of air quality index. If air quality number is between 0 and 30 this is the safe zone. Air quality number between 30 and 50 is alert zone. Air quality between 50 and   100 is danger zone. Air quality between 100 and 120 is emergency zone.

Air pollution can be measured by the air quality index. This tells us the levels of common air pollutants. Depending on where you live, the readings could range from 0-10 or 0-100. The lower the number, the better the air quality.

Go to your local municipal or provincial public health website to find out how your area lists the Air Quality Index. For Ontario, the range is from 0-100.

Check the air quality index before you exercise outdoors. Follow the directions based on the results.

What to do for each air quality category

Air Quality CategoryWhat to do
0 - 30
  • Exercise as usual.
  • Safe to exercise outdoors.
30 - 50
  • Decrease your exercise intensity (slow your walking pace).
  • Watch for signs (such as shortness of breath, increased tiredness).
50 - 100
  • No outdoor exercise.
  • Exercise in an air conditioned environment only.
100 - 120
  • Avoid going outdoors.
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