# What is the Wind Chill Factor?

 Units US       Metric Temperature ° (F or C) Wind Speed (mph or kph)

The wind chill factor, or simply "wind chill," is the phenomenon in which the outside temperature feels colder than what the thermometer reads. We call it wind chill because wind is what primarily makes cold weather feel even more frigid.

To calculate wind chill, you only need to know the current outside temperature and the speed at which the wind is blowing. You can find this information on the news or online weather reports. The formula below will tell you what the outside weather feels like for a given temperature and wind speed. You can also use the convenient wind chill calculator on the left. Choose either US units (degrees Fahrenheit and miles per hour) or metric units (degrees Celsius and Kilometers per hour).

Wind Chill Equation

If the outside temperature is T degrees Fahrenheit and the wind velocity is V miles per hour, then the apparent temperature with wind chill factored in is

35.74 + (0.6215)T - (35.75)V0.16 + (0.4275)TV0.16

Example: Suppose the current temperature is 39°F and the wind speed is 7 mph. Then the felt temperature is

35.74 + (0.6215)(39) - (35.75)70.16 + (0.4275)(39)70.16
= 34

So even though the thermometer reads 39°F, with the wind it feels like 34°F.

For metric units, the wind chill formula is

13.12 + (0.6215)T - (11.37)V0.16 + (0.3965)TV0.16