Felt air temperature

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Felt air temperature (or apparent air temperature) is the air temperature perceived by the body, which may differ from the actual temperature. This is due to other climactic conditions than the actual temperature affecting the exchange of heat between the body and the air. The ability of the air to absorb heat is affected by its relative humidity, and its density. Another parameter is air speed: the faster air blows over a surface, the more air is brought into contact with that surface in a given space of time, increasing the heat loss or gain (depending on the relative temperature of the air) of the body. This phenomenon is calculated into weather reports, with heat index referring to the apparent warmth of air, which is usually higher the denser and more humid it is, and wind chill referring to the reduction of felt air temperature resulting from the velocity of the air. Changing conditions of the body can also affect the apparent temperature. Soldiers, at rest stops after strenuous marching, don heavy clothing to compensate for this.