NASA's Observatorium--Wind Chill: Wind Chill Chart

NASA's Observatorium Wind Chill

Wind Chill Chart

The 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)

The US National Weather Service uses the following formula to calculate wind chill:

WC = 91.4 - (0.474677 - 0.020425 * V + 0.303107 * SQRT(V)) * (91.4 -T)

where:

WC = Wind Chill Index
V = wind speed (mph)
T = temperature (° F)

The wind chill factor, which only affects humans and animals, causes the air to feel colder than it really is. This helps us to understand how cold it feels outside! Moving air carries heat away from the body more effectively than air that is not moving. If there is no wind, the heat radiating from a person's body will stay near the body and warm the air around it. Therefore, the wind chill is simply a means of describing the effect of the movement of air on the heat loss of a person's body.

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Note: The wind chill formula is not valid for wind speeds less than 4 mph. Also, due to rounding conventions used, values may vary slightly from other charts.

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