It may have been warm during the past few days, but if you remember it was extremely cold about a week ago. I enjoy unseasonably warm winter days because when it is warm I do not have to pay ridiculously high heating bills. But, I'm willing to bet that we will have some more extremely cold weather during the next couple of months.

I do not mind cold weather at all. It is supposed to be cold during the winter, and if you are dressed properly and do not have to stay outside very long you can handle the cold just fine. But I really dislike nasty, cold weather. I dread those days when the thermometer hovers around the freezing point, and it rains and the wind blows at the same time. To me, that is miserable weather. At times like that I am thankful for an indoor job instead of a job that requires me to be outside.

When it was so cold last week all of the weather forecasters I watched on television were talking about the wind chill factor. They were telling us that it would be twenty degrees outside, but it would feel like it was ten degrees. For many years I have heard about the wind chill factor. I always understood it to mean that it seems colder than it really is. That was all that mattered to me, because again, I was fortunate enough not to have to work outside. But, I had never stopped to think how the wind chill factors were actually calculated.

After hearing the term wind chill factor several times, I figured I would do a little searching and find out how this term came about, and how the wind chill factor is actually calculated. When I found the answers, I thought maybe you would like to know as well, so let me share what I learned with you.

The wind chill factor is a measure of how much heat your body loses when you factor in the temperature and wind speed. Paul Siple, a geographer and polar explorer, first proposed the use of wind chill factors in 1939. During the 1940's he and another polar explorer, Charles Passel, conducted experiments to determine the amount of time it took water to freeze in plastic cylinders while exposed to various temperatures and wind speeds. They then compared that to the rate that the body loses heat.

Perspiration is a normal body function that regulates the body temperature. The warmer it gets the more you perspire. When a breeze blows over your perspiring body, the perspiration evaporates and you feel cooler.

When it gets cold your body works to try to insulate you. It does this by warming up a thin layer of your skin. When the wind blows, some of this warmth is lost, leaving your skin exposed to the real conditions. Your system will try to build it back up, but the colder it is and the breezier it is, the more the effect is lost and the more your skin temperature drops. That makes you feel colder.

There are other factors that also affect how cold or how warm you feel. Taller and thinner people become colder faster than those that are short and stocky. The elderly are often more cold natured than the young. The kind of clothing you are wearing also affects how cold you feel. And even sunshine on a cold day can actually make you feel warmer, even though it doesn't raise the temperature.

If you know the temperature and the wind speed the easiest way to determine the wind chill factor is to look at a wind chill chart. I have included a condensed version of the chart used by the US National Weather Service. I condensed it because it rarely, if ever, gets below zero degrees in Robeson County, and the wind does not usually blow more than 35 miles per hour.

If you like math and want to figure out the wind chill factor for yourself you can do so. Just use this math formula that was developed by the US National Weather Service: WC = 91.4 - (0.474677 - 0.020425 * V + 0.303107 * SQRT(V)) * (91.4 -T) where WC is the Wind Chill Index, V is wind speed in miles per hour, and T is the temperature in degrees Fahrenheit.

So, the next time you hear your weatherman talking about the wind chill factor you will know exactly what he or she is talking about. You can even check behind them to see if they got the numbers right. Besides, it probably does not matter if they get it right or not. Only weathermen can be wrong almost half the time and still keep their jobs.

E-mail address: Everett_Davis@ncsu.edu

Mailing Address:
P. O. Box 2280
Lumberton, NC 28359-2280

Phone: 910-671-3276
Fax: 910-671-6278

Date Created 06/19/09