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Published February 01, 2013, 05:55 PM

What exactly is windchill?

Fargo, ND (WDAY TV) -- You might not have guessed it when you walked to your car this morning, but today was actually colder than yesterday.

By: Becky Parker, WDAY

Fargo, ND (WDAY TV) -- You might not have guessed it when you walked to your car this morning, but today was actually colder than yesterday.

The difference: yesterday's windchill.

We hear the word all the time, and we know it's going to mean we'll feel colder, the question is, why? What exactly IS wind chill?

When the windchill is 30 below, we know we're going to be very cold but some may not know exactly why.

The windchill index is a complex scientific formula with a practical use.

In a nutshell, it estimates how the conditions will feel on exposed skin.

Daryl Ritchison/WDAY StormTRACKER Meteorologist: "It's just the heat loss based on the wind and whatever the temperature happens to be at that point."

Even when you do head outside with exposed skin, the heat escaping from your body creates a sort of barrier. But when you factor wind into the equation, it effectively blows that protection away.

So, your skin feels colder, but it doesn't make the air any colder.

For instance, on a -10 degree day, your car has the same chance of starting with a thirty below windchill as it does with no wind.

Daryl: "You cannot cool an object down below its air temperature."

But the purpose of the windchill isn't just to let you know you'll be shivering all day. It lets you know you need to dress for that temperature because windchill accelerates frostbite.

Dr. Robert Martino/Sanford: "Skin tissue starts to freeze once you get into the 20s with exposure. But that's going to happen much quicker if you add on the factors of wind, moisture, contact with cold surfaces."

So, that scientific formula using temperature and wind speed could save your skin, and maybe some fingers and toes. There are many variables with wind chill.

Radiation from the sun is not factored into the equation, so that could make you feel warmer than the wind chill would suggest.

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