Equivalent Wind Chill Temperatures

To determine wind chill, find the outside air temperature on the top line, then read down the column to the measured wind speed (MPH - Miles Per Hour.) For example: When the outside air temperature is 0 degrees F, and the wind speed is 20 MPH the rate of heat loss is equivalent to -39 degrees F when there is no wind (zero up to 4 mph.)

The area shown in green corresponds to Little Danger. The area shown in yellow corresponds to Increasing Danger where flesh may freeze within 1 minute. The area show in red corresponds to great danger where flesh may freeze within 30 seconds.

source and more info : edu