As temperatures plummet and the winds howl this winter, you will hear more and more about the dangers of the “wind chill.” What is wind chill, and why is it important to understand how it affects us?
As USA Today reports, the wind chill temperature is how cold people (and animals) feel while outside. Wind chill is based on the rate of heat loss from exposed skin caused by the combination of wind and cold, according to the National Weather Service (NWS).
As the wind increases, it draws heat from the body, driving down skin temperature and eventually the body’s internal temperature. “It’s how it feels when you’re out in cold weather with wind blowing,” Bob Oravec, a lead forecaster for the Weather Service at the Weather Prediction Center, told Popular Science.
What do wind chill numbers mean?
Therefore, the wind makes it feel much colder than it really is, so it’s been described as a “feels-like” number. If the temperature is 0 degrees and the wind is blowing at 15 mph, the wind chill is 19 degrees below zero.
Low wind chill numbers shouldn’t keep you from going out, but they should encourage you to dress properly. For example, when the wind chill is around 40 degrees below zero, exposed skin can freeze in as little as 10 minutes.
How long can you be in wind chill?
Remember that the wind chill temperature is not some different kind of temperature: Wind chill alone can never make an object colder than the air temperature. Even if the wind chill is 10 degrees, you won’t get frostbite or freeze your car’s radiator if the air temperature is 32 degrees or above.
The Weather Service began to include wind chill in their forecasts in the early 1970s, several decades after Antarctic explorers first published research about it in the late 1930s.
The U.S. and Canadian weather services revised the wind chill index in 2001, based on greater scientific knowledge and on experiments that tested how fast the faces of volunteers cooled in a wind tunnel with various combinations of wind and temperature.
Calculating Wind Chill
Direct Measurement vs. Calculation:
According to meteorologists at Mount Washington Observatory, air temperature can be measured directly, using any type of thermometer. This is an absolute value; a distinct characteristic of the air.
Wind chill, on the other hand, is a calculated value from two distinct environmental factors: air temperature & wind speed. Wind chill cannot be directly measured, as it is not a distinct characteristic of the air.
Absolute vs. Conditional: Air temperature is an absolute measurable value. Wind chill is an apparent factor; that is, what the air temperature “feels like” when you add the wind to it. There is no instrument with which you can measure wind chill, and it is dependent on several factors, such as the presence of wind speed and exposed human skin.
Human-Biased: Air temperature is the same for all objects exposed to a particular air mass at a certain moment in time. Wind chill, however, is geared specifically towards human exposure.
A Misnomer
When meteorologists report temperatures in any way, shape, or form, they are ALWAYS referring to ambient air temperature. A professional meteorologist will never pass off a wind chill as air temperature—it can be misleading and even dangerous to do so.
The statement “the temperature with the wind chill is…” is a misnomer. Temperature does not change because of an increase in wind speed. Although related, temperature and wind chill are two completely distinct environmental characteristics.
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