When I was hiking in the mountains this past weekend, the temperatures were in the mid-thirties to lower forties, but felt much colder. There was still a lot of snow on the ground and the wind was blowing steadily on the ridges I was hiking over at an elevation of about 2000 ft. I got to thinking about wind chill and decided to research it when I got back from my trip. Apparently there has been a revolution in the way that wind chill is calculated over the past few years based on new research performed by the Canadian government that has been adopted here in the United States as well.
Wind chill can best be described as a sensation that we feel as a result of the effects of wind and temperature. Wind chill is not something that can be measured using a device, so scientists have come up with a mathematical formula that relates wind speed and air temperature to the cooling sensation we feel on human skin.
Prior to 2001, wind chill was calculated based on the time it took for a cylinder of water to freeze in the wind based on experiments conducted in Antartica in 1939. During 2001 a team of scientists from Canada and the US decided to develop a new wind chil index that is based instead on the lost of heat from peoples' faces, the part of the body most likely to be affected by wind chill. Wind chill does not impact inanimate objects like automobiles or tents because they objects cannot cool below the actual air temperature.
Understanding wind chill is particularly important to the prevention of frostbite and hypothermia. As wind speed increases the body is cooled at a faster rate causing one's skin termpertaure to drop. If your body is wet, wind can speed up the evaporation process and draws more heat away from you body. Studies show that when your body is wet, it loses heat much more rapidly than when it is dry.
The best way to protect yourself against wind chill is find shelter and get out of the wind. If you are wet, change clothing, or remove clothes if you are sweating during strenuous activities such as hiking. When the wind chill is high, try to cover as much exposed skin as possible, particularly on your head where up to 40% of body heat is lost. Wear a wind resistant outer layer like a shell and cover your hands and feet with mittens that cover your wrists and boots.
For more information, including ways to forecast wind chill by yourself based on the movement of trees in the wind, see: