Tuesday, December 21, 2004

Apple #14: Wind Chill


It's been really freakin' cold the past few days. When people talk about the wind chill, I think, that's just a way for them to feel less like pansies when it's cold outside. But it turns out, it's actually kind of a crucial indicator.
  • Wind chill is an indicator of how cold the air actually feels. Moving air carries heat away from the body. If there is no wind, the heat from your body will stay and warm the air around you. Therefore, when the wind speed is 3 mph or less, it is possible for the wind chill to be warmer than the actual temperature.
  • Wind chill is derived by a somewhat complex calculation based on temperature times wind speed. See the actual calculation.
  • The method for calculating wind chill was first developed in the 1940s. This method was changed in 2000 after some abnormally mild winters followed by an unusally cold winter in Canada and the northern US, which made for somewhat strange wind chill readings.
  • When wind speeds get high enough and temperatures drop low enough, you get into frostbite zone. For example, when it's 10 degrees F and the wind is traveling at 55 mph (yes, that's fast), you can get frostbite in 15 minutes or less. That's no joke.
  • In Antarctica, winds have been recorded as high as 200 mph. In July in 1983, the temperature dropped to -129 Fahrenheit. That's the coldest recorded temperature in the world. If those two situations were combined, the wind chill would be -257 F.
  • For the past 12 hours, wind chills in Springfield, MO (to pick a random city) have been between 25 degrees F and 33 degrees F.

Environment Canada's wind chill history page
Antarctic Connection
Medline article on
National Weather Service Forecast Office for
Springfield, MO

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