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What is wind chill?

Wind chill is based on the rate of heat loss from exposed skin caused by the combined effects of wind and cold. As the wind speed increases, heat is carried away from the body at an accelerated rate, driving down the body temperature. The wind chill temperature, an "apparent" temperature, gives us a better estimate of how cold it really feels outside. The measure of the rate of heat loss based on air temperatures and wind speeds is not a temperature, but it allows us to understand how quickly heat is lost to the wind.

Why should we care about wind chill?

A lower wind chill can increase the rate at which certain cold-weather dangers, such as frostbite and hypothermia, can develop.

Wind Chill Temperature

Calculating Wind Chill

Wind chill index is based on an equation first proposed in 1939 by Paul Siple, a famous geographer, polar explorer, and an authority on the Antarctic. In the 1940s, he and fellow Antarctic explorer Charles F. Passel conducted experiments on the amount of time it took for water to freeze in a plastic cylinder while exposed to the elements. They discovered that the time it took for the water to freeze depended on the initial temperature of the water, the outside air temperature, and the speed of the wind. This was the original formula: H = (10.45 + 10 sqrt (v) - v) (33-t) where: H = heat loss(in kilocalories per square meter-hour) V = wind speed (meters per second/mps) T = temperature (° C). Click here to calculate the wind chill factor.

(Sources: NASA's Observatorium and National Weather Service)