The apparent (or "feels like
") temperature (°C) is the perceived temperature, which people experience
under the forecast conditions. It is composed of a heat index
and a wind chill factor
. The heat index
(HI) calculates the temperature the body feels when heat and humidity are combined; it rises with actual air temperature and relative humidity, which make it increasingly difficult for the body to remove the excess heat through sweating. Exposure to direct sunlight can increase the HI by up to 10°C. When the heat index exceeds 37°C, the body will need extra help for removing heat to avoid heat stress and collapse. The wind chill factor
calculates how much heat is removed from the body through air movement. It generally reduces perceived temperature compared to the actual.
The meteoblue "feels like" temperature is a combination of both effects. Under windy conditions, the perceived temperature is lower than the actual temperature. Under moist (and mostly hot) conditions, the perceived temperature is higher than the actual temperature - conditions are then is described as "muggy" and occur mainly during summer and in the tropics, principally around the equator (e.g. in Indonesia, Kenia, Ruanda, Congo, Brazil, Peru).