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© Copyright 2002, Jim Loy
The following is a wind chill (or windchill) factor (or index) chart from the National Weather Service (this chart has changed slightly, over the years):
| Temperature (degrees Fahrenheit) | |||||||||||||||||
| mph | 35 | 30 | 25 | 20 | 15 | 10 | 5 | 0 | -5 | -10 | -15 | -20 | -25 | -30 | -35 | -40 | -45 |
| 5 | 33 | 27 | 21 | 16 | 12 | 7 | 0 | -5 | -10 | -15 | -21 | -26 | -31 | -36 | -42 | -47 | -52 |
| 10 | 22 | 16 | 10 | 3 | -3 | -9 | -15 | -22 | -27 | -34 | -40 | -46 | -52 | -58 | -64 | -71 | -77 |
| 15 | 16 | 9 | 2 | -5 | -11 | -18 | -25 | -31 | -38 | -45 | -51 | -58 | -65 | -72 | -78 | -85 | -92 |
| 20 | 12 | 4 | -3 | -10 | -17 | -24 | -31 | -39 | -46 | -53 | -60 | -67 | -74 | -81 | -88 | -95 | -103 |
| 25 | 8 | 1 | -7 | -15 | -22 | -29 | -36 | -44 | -51 | -59 | -66 | -74 | -81 | -88 | -96 | -103 | -110 |
| 30 | 6 | -2 | -10 | -18 | -25 | -33 | -41 | -49 | -56 | -64 | -71 | -79 | -86 | -93 | -101 | -109 | -116 |
| 35 | 4 | -4 | -12 | -20 | -27 | -35 | -43 | -52 | -58 | -67 | -74 | -82 | -89 | -97 | -105 | -113 | -120 |
| 40 | 3 | -5 | -13 | -21 | -29 | -37 | -45 | -53 | -60 | -69 | -76 | -84 | -92 | -100 | -107 | -115 | -123 |
| 45 | 2 | -6 | -14 | -22 | -30 | -38 | -46 | -54 | -62 | -70 | -78 | -85 | -93 | -102 | -109 | -117 | -125 |
And we are told that wind speed greater than 45 mph have little additional chilling effect. I'm sure there are wind chill tables for the metric system. To use the chart, just line up the wind speed with the temperature, to get the temperature as it seems to a human. For example if it is -10 degrees and 25 mph, then the wind chill is -59. In other words it seems like it is -59 degrees Fahrenheit. The wind takes heat away from your body.
We are also told that a wind chill of -20 degrees presents little danger. -21 to -74 may cause flesh to freeze within a minute. And -75 or colder may cause flesh to freeze within 30 seconds.
The title of the book Minus 148 Degrees: The Winter Ascent of Mt. McKinley by Art Davidson, is based upon a wind speed of 130 mph and a temperature of -30F to -40F. Apparently someone extrapolated the temperature for a wind speed that was off the chart. These folks lost most of their fingers and toes.