January 7, 2014 6:50 pm

Wind chill: how it’s measured and how it affects you

Watch the video above: What wind chill is and how it affects you. Sean Mallen reports. 

TORONTO – Temperatures dipped below -20 degrees Celsius Tuesday but felt closer to -30 or -40 degrees due to one typically annoying measurement: wind chill.

READ MORE: Will this be Canada’s coldest winter?

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The wind chill, as the name might suggest, measures how much colder the human body will feel when assaulted by the wind.

“Wind chill itself is a very good measurement because it’s trying to include both the absolute air temperature and wind,” Dr. Stephen S. Cheung, a Canadian Research Chair in Environmental Ergonomics said. “Both of them are going to have an effect on how fast your body cools.”

The absolute air temperature is the base temperature. On Tuesday, it dipped below – 20 degrees Celsius in Toronto.

READ MORE: Toronto under extreme cold weather alert

But the wind also has an effect. As Cheung explains, everyone has an “invisible layer” of air surrounding them that their body is heating up. But the more aggressive the wind, the faster that cocoon of warmth is literally pushed away.

“You warm up this air right next to you, and then [wind] removes it,” he said. “So what you constantly have to do is replace that warm air. So you’re constantly losing heat a lot faster that way. So the faster the wind, the greater rate at which you’re going to lose heat.”

How is wind chill measured?

Scientists have developed the “wind chill index” or a measure of how the wind will affect a person’s feeling of warmth.

Prior to 2002, scientists in Antarctica measured wind chill by placing vials of water outside in different temperatures and at different wind speeds. They then measured how long it took for the vials to freeze.

READ MORE: Why extreme weather stops us cold

After 2002, scientists at the Department of National Defence Research Centre in Toronto began using the physiological reaction people had to different wind speeds.

“In 2002, the new scale came out and that was actually based on human subjects and at very cold temperatures, at different temperatures, different air speeds, they took the subjects right to the edge of being the initial stages of cold injury or frostbit,” Cheung said.

How to protect yourself

Some animals – bears and seals for example – have acquired ways of coping with extreme cold temperatures - hibernation or a thick layer of blubberrespectively.

But human beings, lacking both of those traits (thankfully) have something else: behaviour.

“What we do have to compensate, is the ability to have behavioural strategies, the first thing is building shelter, building clothes,” he said.

But his best tip on fighting the cold is a simple one: don’t go outside.

“That’s still the best advice on days like this, if you don’t need to go out, don’t,” he said.

But if you do have to go outside, remember, your choices can keep you warm. Dress in layers, make sure you’re wearing dry clothes, wear fabrics that wick away sweat and wear a hat.

READ MORE: Arctic cold engulfs the country

Most importantly, Cheung said, protect your hands and feet.

“Your body is somewhat of a heat hog, it’s going to try to prioritize keeping blood in your core and in your chest, so the first thing that’s going to happen when you’re out in the cold is you’re going to have less blood flow to the skin and to your limbs, your hands and your feet.”

- With files from Sean Mallen

© Shaw Media, 2014

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