Humidex is used as a measure of how hot we feel. It expresses the combined effects of warm temperatures and humidity, and provides a number that describes how hot people feel, in a similar way that the equivalent chill temperature or wind chill factor describes how cold people feel.

The relation between humidex and comfort is subjective, and varies widely between individuals. Environment Canada provides the following guide as a measure of discomfort according to humidex:

Humidex Range Degree of Comfort
20-29°C most people are comfortable
30-39°C people experience some discomfort.
40-45°C people are uncomfortable; avoid exertion
above 45°C dangerous conditions exist and many types of labour must be restricted.
above 54°C heat stroke imminent

* The American Society of Heating, Refrigerating, and Air Conditioning Engineers (ASHRAE) Standard "Thermal environmental conditions for human occupancy" recommends temperature ranges of 20°C to 26°C at 50% relative humidity as comfortable for sedentary work. An air temperature of 26°C at 50% relative humidity corresponds to a humidex of 29°C.

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