What is Wind Chill?

What is Wind Chill?

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 Antarctica in 1939. In 2001 a team of scientists from Canada and the US decided to develop a new wind chill index that is based instead on the loss of heat from people’s’ 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 are objects that 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 temperature to drop. If your body is wet, wind can speed up the evaporation process and draws more heat away from your body. Studies show that when your body is wet, it loses heat much more rapidly than when it is dry.

National Weather Service Wind Chill Chart
The best way to protect yourself against wind chill is to 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 with mittens that cover your wrists.

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  1. I didn't know that was how wind chill was calculated. Thats a pretty cool little tidbit of historical info. Wind chill really does make a huge difference as does humidity. Out west here there is very little humidity which affects how cold it feels outside.

  2. It amazing how much you can learn while writing a blog. I didn't know it either until I'd researched it.

  3. Windchill was explained to me in the following manner. Curious if it fits with what you learned.

    Your body is constantly working to keep a thin layer of warm air along your entire body. When it is windy & you don't have the correct layers on, that warm air layer is stripped away by the wind and your body will expand a lot of energy trying to re-establish the warm air layer.

    So, in addition to the risk of cold injury, wind chill can rapidly sap your energy level.

  4. Standard heat loss from the head is ~7%. It can peak up to 50% during high output exercise, but only for a very brief period. The only other exception is when shivering during hypothermia, in which case it can hit up to 55%.

  5. Tom, I'm not sure I believe the warm layer of air theory in this form. Could you have taken this out of context? It sounds like an explanation for how a vapor barrier works, but you'd substitute the word "warmth" for "humidity".

  6. That new chart looks so user-UNFRIENDLY. Maybe it's me, but I don't see a workable way to calculate wind chill in the field in your head, like could be done with the old system. This new system looks to me like you need to have the chart with you?

  7. Most people with a beard (including myself) will attest that having a beard helps significantly with wind chill in the winter however, I have not been able to find any scientific evidence to back this up. I am assuming it would have more to do with the moisture wicking properties versus insulation. Any thoughts?