https://en.wikipedia.org/wiki/Humidex

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.