The
heat index (
HI) or
humiture or
humidex (not to be confused with the
Canadian humidex) is an index that combines
air temperature and
relative humidity in an attempt to determine the human-perceived equivalent temperature—how hot it would feel if the humidity were some other value. The result is also known as the "felt air temperature" or "
apparent temperature". For example, when the temperature is with very high humidity, the heat index can be about .