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Humidex calculator
The humidex is Canada's measure of how hot humid weather feels. Enter the temperature and either the humidity or the dew point.
Humidex ranges (Environment and Climate Change Canada)
| Humidex | Degree of comfort |
|---|---|
| 20 to 29 | Little discomfort |
| 30 to 39 | Some discomfort |
| 40 to 45 | Great discomfort; avoid exertion |
| 46 and over | Dangerous; possible heat stroke |
How it is worked out
Environment Canada's formula: humidex = air temperature + 0.5555 × (e − 10), where e is the water vapour pressure in hectopascals, calculated from the dew point. If you enter the relative humidity instead, we first work out the dew point with the Magnus formula. A humidex over 40 is extremely high: cut out all unnecessary physical activity. Over 30, limit or change outdoor exercise.
The US uses the heat index instead; the two are similar but not the same scale.
For planning and general information. In an emergency, follow the instructions of your local authorities and call your emergency number (911, 112, 999 or 000).
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Source: Environment and Climate Change Canada, Climate glossary (Humidex) and How to use the Humidex.