Share it! Science : Brrrrrr! Understanding the Wind Chill Factor

Monday, February 16, 2015

Brrrrrr! Understanding the Wind Chill Factor

Oh, winter. The high temperature at my house today is supposed to reach 7 degrees Fahrenheit. This does not take into account the effect of the wind. Granted, we are at near record breaking lows, but at this point, a 25 degree day would feel balmy! There is always a lot of talk and concern over the cold temperatures in the winter, but also of the wind chill factor. We all understand that the wind chill makes it feel colder than the thermometer is reading and that it can be dangerous to exposed skin, but what exactly is the wind chill factor and how do we calculate it?

(photo credit: 416style)
The wind chill factor is derived from a mathematical equation that takes into account the wind speed and the temperature. It calculates how cold your body perceives the temperature to be. This is important because a significant drop in skin temperature will cause your body to close down blood vessels in the skin. Scientists believe this is a protective mechanism to keep the organs in the body's core warm so that you stay alive. As far as your brain is concerned, losing a finger to frostbite is worth saving your life. (I agree, thanks, brain!)

When you step out on a chilly day your skin temperature does not dip down to the ambient temperature of the air. Your body radiates heat that keeps a thin layer of warm air around your skin. When there is no wind, your skin is more capable of staying warmer than the ambient temperature. Once the wind speeds up it blows this warm insulating air layer away from your skin. The faster the wind, the faster this heat loss occurs. When the wind speeds go beyond about 25 miles, your body can no longer keep up and your skin is exposed to the actual low temperature of the ambient air.
"Toboggan Party" (photo credit: Library of Congress)
Calculating and reporting the wind chill factor is not a very accurate science, but it does serve as a gauge for understanding how to dress for the elements and which outdoor activities may be safe in the cold. The equations for calculating the wind chill have been amended over the years. The idea for the wind chill factor was invented back in the 1940's by Antarctic explorers. They hung bottles of water on a long post and measured how long it took them to freeze in different temperature and wind speed conditions.

Their findings and subsequent equation didn't accurately portray human skin or the benefits of any sort of insulative clothing. In fact, when they tried to amend their equations they got some weird results, including temperatures that supposedly rose when the wind blew faster. In the early 2000's scientists from the United States and Canada came up with a completely new formula that took into account the properties of human face.

It is still not an exact science as we are all different, and this measure does not take into affect the sunshine or other weather-related factors. In general the equation was still an improvement as it gives more realistic numbers. To determine the wind chill factor, you can use the actual equation, or a wind chill table. Several wind chill calculators and tables can be found in the resources links below.

Basically the most important thing to understand is that the wind chill factor is a measure created by meteorologists and is not the actual temperature, it is the temperature we perceive. That said, the wind chill does have an affect on our bodies and can be dangerous to exposed skin. It is not something to be taken lightly! Keep warm out there!


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Wind Chill Resources and Activities:


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