Meteorology

What Does Wind Chill Even Mean? Not What You Think

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You wake up on a frigid winter morning and check the weather on your phone. It says it's 38 degrees Fahrenheit (3 degrees Celsius) outside with a wind chill of 31 degrees Fahrenheit (negative one degree Celsius). So, freezing. But when you look out the window, you can clearly see puddles of liquid water. Not freezing. What's up with that? This is what: wind chill doesn't tell you whether it's freezing outside; it just predicts how fast you'll get frostbite. And, as it turns out, it's even pretty lousy at that.

How Wind Chill Began

The first idea of a "wind chill" factor was developed by a pair of American scientists working in Antarctica who wanted to measure how wind was able to make objects lose heat more quickly than they would usually. (To do this, they used the solidly scientific method of leaving plastic water bottles on the roof of their hut). Because they expressed this new metric in kilocalories per hour per square meter, it was mostly used by scientists until the 1960s. Then, the U.S. military realized it might come in handy for the troops, and translated the metric into "equivalent temperature"—that is, degrees Fahrenheit. That's when it caught on like wildfire, appearing in TV and radio weather reports everywhere.

Still, this water-bottle metric was unrealistic to use on humans, so the National Weather Service recruited scientists to revise the wind-chill formula by using experiments with real people. It was brilliant in its simplicity: if you know the temperature and wind speed outside, you can know your risk of frostbite. Kind of.

Why Wind Chill Blows

Here's the problem: it assumes a whole lot of things that probably don't apply to you. Wind chill only predicts your risk of frostbite if you're 5 foot 6, overweight, the sun isn't shining, you have no trees or buildings blocking the wind, and you're walking steadily at 3 miles per hour straight into a headwind. Pretty specific. Despite this glaring flaw and many calling to abandon the metric, the National Weather service still promotes wind chill as the be-all end-all.

Luckily, there are better alternatives out there. If you use Accuweather, you can check its RealFeel temperature to know how it feels outside. And for a more scientific measure, try the Universal Thermal Climate Index (UTCI).

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Written by Ashley Hamer January 3, 2017

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