If you’ve ever listened to a weather report in the wintertime, you have probably heard forecasters talk about the “wind chill.” Wind chill is the measurement that tells you how cold your body will feel when you’re outside. It takes into account the actual temperature, as well as the speed of the wind. For example, if the temperature is 10°F, you will feel colder if the wind is blowing at 30 miles per hour than if the wind is blowing at 5 miles per hour. Thus, the wind chill temperature will be lower on the windier day.
In the fall of 2001, the National Weather Service revised their wind chill formula. The old formula was based on experiments done in 1945. The new formula is based on modern heat-transfer theory and experiments done in a chilled wind tunnel in Toronto, Canada. In the experiments, the faces of several men and women were exposed to different combinations of temperatures and winds. Scientists measured how fast the temperatures of the exposed skin dropped. They used their results to develop the new wind chill chart. A portion of the chart is shown below:
From the chart you can see that on a day when the temperature is 10°F and the wind is blowing at 5 miles per hour, the wind chill is 1°F. How much warmer is this than if the wind were blowing at 30 miles per hour?
On the old wind chill chart, the wind chill at 30 miles per hour on a day when the temperature was 10°F was 33 degrees below zero. How much colder is this temperature than the corresponding wind chill measurement on the new scale?