Humidex is a term to measure how hot we feel. Weather forecasters use the humidex to describe when heat and humidity combine at uncomfortable or dangerous levels.

Environment Canada’s Humidex Comfort Ratings (Celsius)

Environment Canada developed a humidex rating chart to announce when heat and humidity may be uncomfortable to people. (Click image below to enlarge)


Why is humidex important?

When it is hot and humid, it is more difficult for you to cool down by sweating. When the relative humidity reaches around 90%, your sweat does not evaporate. In these situations, your body temperature may rise and lead to heat rash, cramps, heat exhaustion and heat stroke.

“Humidex Rating and Work,”, Canadian Centre for Occupational Health and Safety, July 28, 2008, Reproduced with the permission of CCOHS,

Environment Canada

For more information on working under hot conditions, see the WorkSafe publications, Working Under Hot Conditions and Hot Conditions Guidelines, below:

Working Under Hot Conditions
Hot Conditions Guidelines