How are wind chills calculated? A meteorologist breaks down the formula.
CHICAGO (CBS) — In the Windy City, wind chill is a term we often use to describe how cold it feels to us as soon as we step outside.
The wind chill is based on the rate of heat loss from exposed skin caused by cold air and wind. When winds increase, heat is carried away from us at a faster rate, chilling the body temperature down. Just like blowing on hot food to cool it down.
Different parameters go into calculating the wind chill temperature index, and this is the fancy wind chill equation that you could mathematically solve to get the wind chill values.
Wind Chill (F) = 35.74 + 0.6215T – 35.75 (V^0.16) + 0.4275T(V^0.16)
T= Air Temperature (F) V= Wind Speed (mph)
The wind chill temperature index has a lot of important parameters that go along with calculating it, like using wind speed observed at 5 feet, the average height of a human face, rather than a standard anemometer height.
However, if you don't want to solve the equation's acrobatics, this wind chill chart from the National Weather Service highlights all the components, including air temperature, wind, and apparent wind chill values.
Along the X-axis or the top are temperatures in Fahrenheit. The Y-axis or down the side is wind speed in miles per hour. For example, taking an air temperature of 20 degrees with a wind speed of 20 mph. Connect those numbers in the middle, which gives the wind chill temperature of 4.
The colors on the chart represent the frostbite time of exposed skin outside. In our example, frostbite could happen in about 30 minutes.
Once the cold weather forecast reaches a certain threshold, the National Weather Service is expected to issue an Extreme Cold Watch/Warning or a Cold Weather Advisory. If they do, your First Alert Weather team will let you know.
Wind chill is not a true temperature, but it allows us to understand how heat is lost due to the wind.
Everyone also has a different tolerance to the cold as well, so this is not exact, but it gives us a good indication of how it will feel outside not only to us, but animals too.
With winter fast approaching and this week's cold snap in Chicago, make sure to stay warm and get the latest forecast everyday with CBS News Chicago.