Editing Heat index (section)

{{short description|Temperature index that accounts for the effects of humidity}}
{{humidity}}
The '''heat index''' ('''HI''') is an index that combines [[air]] [[temperature]] and [[relative humidity]], in [[shade (shadow)|shaded areas]], to posit a human-perceived equivalent temperature, as how hot it would feel if the [[humidity]] were some other value in the [[Shade (shadow)|shade]]. For example, when the temperature is {{convert|32|°C}} with 70% relative humidity, the heat index is {{convert|41|°C}} (see table below). The heat index is meant to describe experienced temperatures in the shade, but it does not take into account heating from direct sunlight, physical activity or cooling from wind. 

The human body normally cools itself by [[evaporation]] of [[perspiration|sweat]]. High relative humidity reduces evaporation and cooling, increasing discomfort and potential [[Hyperthermia|heat stress]]. Different individuals perceive heat differently due to body shape, metabolism, level of hydration, [[pregnancy]], or other physical conditions. Measurement of perceived temperature has been based on reports of how hot subjects feel under controlled conditions of temperature and humidity. Besides the heat index, other measures of [[apparent temperature]] include the Canadian [[humidex]], the [[wet-bulb globe temperature]], "relative outdoor temperature", and the proprietary "[[AccuWeather#RealFeel temperature|RealFeel]]".