Let's say you read the thermometer on your outside porch, or call the Time and Temperature number provided by your local phone company. And you find out that the temperature is 40 degrees (F). You and your students dress accordingly. But when you get outside, it feels like an Arctic Northerner is blowing in with all the trimmings. What happened? Did you read the thermometer wrong? Are the guys at the phone company losin' it?

So what is it that can make a 40 (F) degree day seem like it's 28 degrees outside? A 10 mile-per-hour wind!

In 1939, Paul A. Siple, an Antarctic explorer, first called it 'the wind chill factor'. This is when the air motion (wind) around us can cause us to loose some of our body heat.

What makes this situation dangerous is that when we hear that the temperature is 40 degrees outside, we might not dress warm enough.

So, the next time you hear your local temperature, find out what the wind chill factor is. It might make the difference between one sweater or two.

Below you'll find a chart that shows you just how much difference a cold wind can make, even on a sunny day.

For another example: a 20 mile per hour (mph) wind can turn a 50° day seem like it's 36°. That's almost freezing! Brr!

                                                  TEMPERATURES IN FAHRENHEIT

                        WIND SPEED         50°              40°              30°

                             5mph                 48°               37°               27°
                 
                            10mph                 40°               28°               16°

                            20mph                 36°               22°               9°