Humidex – an abbreviation for Humidity Index – refers to the perceived temperature based on the measured air temperature and relative humidity or dew point.
Humidex is a value used by Canadian metereologists to describe the influence of measured air temperature and humidity on the human body.
- 20 to 29: Little to no discomfort
- 30 to 39: Some discomfort
- 40 to 45: Great discomfort; avoid exertion
- Above 45: Dangerous; heat stroke quite possible
Humidex acquires its significance at air temperatures above about 20 to 25 °C. For air temperatures below about 10 °C, instead of humidity, wind speed is more important for the perceived temperature, which is expressed in the measure of Windchill.