The windchill factor is the temperature of windless air that would have
the same effect on exposed skin as the combined effects of wind speed
and air temperature.
Increased wind speeds result in accelerated heat loss from exposed
skin, since it reduces the boundary layer of stagnant warm air on the
skin. This stagnant air film acts as an insulator. When this
insulation layer is reduced, the body will lose heat more rapidly.
On November 1, 2001 a new windchill temperature index was implemented by the National Weather Service.
This new formula to calculate windchill is:
Wind Chill (F) = 35.74 + 0.6215 T - 35.75(V0.16) + 0.4275T(V0.16)
where V is the wind speed in miles per hour, and T is the outside temperature in degrees Fahrenheit.
Windchill temperatures (F) as a function of air temperature (F) and wind speed (mph):
Temperature (F)
45 40 35 30 25 20 15 10 5 0
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5 | 42 36 31 25 19 13 7 1 -5 -11
10 | 40 34 27 21 15 9 3 -4 -10 -16
15 | 38 32 25 19 13 6 0 -7 -13 -19
Wind 20 | 37 30 24 17 11 4 -2 -9 -15 -22
Speed 25 | 36 29 23 16 9 3 -4 -11 -17 -24
(mph) 30 | 35 28 22 15 8 1 -5 -12 -19 -26
35 | 35 28 21 14 7 0 -7 -14 -21 -27
40 | 34 27 20 13 6 -1 -8 -15 -22 -29
45 | 33 26 19 12 5 -2 -9 -16 -23 -30
50 | 33 26 19 12 4 -3 -10 -17 -24 -31
55 | 32 25 18 11 4 -3 -11 -18 -25 -32
60 | 32 25 17 10 3 -4 -11 -19 -26 -33
Temperature (F)
-5 -10 -15 -20 -25 -30 -35 -40 -45
------------------------------------------------------
5 | -16 -22 -28 -34 -40 -46 -52 -57 -63
10 | -22 -28 -35 -41 -47 -53 -59 -66 -72
15 | -26 -32 -39 -45 -51 -58 -64 -71 -77
Wind 20 | -29 -35 -42 -48 -55 -61 -68 -74 -81
Speed 25 | -31 -37 -44 -51 -58 -64 -71 -78 -84
(mph) 30 | -33 -39 -46 -53 -60 -67 -73 -80 -87
35 | -34 -41 -48 -55 -62 -69 -76 -82 -89
40 | -36 -43 -50 -57 -64 -71 -78 -84 -91
45 | -37 -44 -51 -58 -65 -72 -79 -86 -93
50 | -38 -45 -52 -60 -67 -74 -81 -88 -95
55 | -39 -46 -54 -61 -68 -75 -82 -89 -97
60 | -40 -48 -55 -62 -69 -76 -84 -91 -98