Weather Whys; Chill Factor

This is weather wise. The wind chill factor is an often misunderstood component of your local weather report. Though chill factors of below freezing may tingle your toes and bite your nose, your garden isn't necessarily in danger. The chill factor was first calculated by Dr. Paul Cypill in 1939. He developed it after observing the effects of wind and temperature on humans who were stationed in Antarctica. Cypill found that the body surrounds itself with a thin layer of warm air. That's why on a cold day, if winds are calm, you may feel warmer than the thermometer would lead you to believe. When the wind is blowing, that insulating layer is swept away, forcing the body to use up more heat. So generally, for a particular temperature, the body will lose more heat with a faster wind. For instance, if the temperature outside is 40 degrees, a wind speed of 10 mph will make it feel like 30 degrees, while a wind speed of 30 mph will make it feel like 10 degrees.

Those figures may lead one to assume that the wind chill temperature equals the current temperature minus the wind speed, but it's not that easy. The combination of lower temperatures and higher wind speeds magnifies the effect. For instance, a temperature of 0 combined with a wind speed of 15 mph gives a wind chill factor of minus 30. Very low wind chill factors can remove enough heat from the body to cause dangerous hypothermia. But unless the air temperature itself is below freezing, your plants won't freeze. And neither will you. We'd like to know what you think of weather-wise. Please write us at Weatherwise, KGOU Radio, the University of Oklahoma. Norman, Oklahoma, 73019-0250. For weather-wise, I'm Drew Barlow.