What is “wind chill” all about?

Dear Straight Dope: What is the REAL meaning of wind chill? This confuses me. I was told that if it is 20 below with a windchill making it 30 below the absolute temperature is still 20 below. So what does the windchill have to do with anything? Thanks, Troy Ives

Veg replies:

The real meaning of wind chill, Troy, isn’t that wind actually decreases the temperature, it’s that wind makes our skin feel as though the temperature is lower than it really is due to a process known as transpo-evaporation. When moisture evaporates, the surface from which it evaporates loses some heat. Even if you didn’t just emerge from a quick dip in the Baltic Sea, there is always moisture on your skin; that’s just the way it is with us humans.

When the wind hits it, the evaporation process is sped up, so your body loses heat more quickly than it would normally at the current temperature, making your brain think that it’s actually colder out than it really is.

Got a chart here that shows the windchill for various air temps and wind speeds and such. But we get paid on a piecework basis on this job. So if you wanna see it, you’re going to have to ask.

Veg

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What is “wind chill” all about?

A STAFF REPORT FROM THE STRAIGHT DOPE SCIENCE ADVISORY BOARD