Wind Chill Table Wind Chill Index - Wind chill is based on the rate of heat loss from exposed skin caused by the combined effects of wind and cold. As the wind speed increases, heat is carried away from the body at an accelerated rate, driving down the body temperature. The wind chill temperature, an "apparent" temperature, gives us a better estimate of how cold it really feels outside. The measure of the rate of heat loss based on air temperatures and wind speeds is not a temperature, but it allows us to understand how quickly heat is lost to the wind.
  Wind chill: A rough guide to danger
Wind chill applies only to people and animals As temperatures fall and the wind howls, we begin hearing about the danger of "wind chill." The wind chill index, shown above, combines the temperature and wind speed to tell you how cold the wind makes it "feel." Even though the chill is given as a temperature, it's not really a different kind of temperature. It's based on polar research going back to the early 1940s and is meant to be a guide to how much you should bundle up when going outside. Low wind-chill numbers shouldn't keep you from going out; they should encourage you to dress properly, however. Meteorologists and other scientists have raised scientific concerns about the whole idea of wind chill. 
Information about Wind Chill Doubts and Conflicts The wind chill formula, its development

The term "wind chill" goes back to the Antarctic explorer Paul A. Siple, who coined it a 1939 dissertation, "Adaptation of the Explorer to the Climate of Antarctica." During the 1940s Siple and Charles F. Passel conducted experiments on the time needed to freeze water in a plastic cylinder that was exposed to the elements. They found that the time depends on how warm the water is at the beginning, the outside temperature and the wind speed.

The formula the National Weather Service uses to compute wind chill is:
T(wc) = 0.0817(3.71V**0.5 + 5.81 -0.25V)(T - 91.4) + 91.4

T(wc) is the wind chill, V is in the wind speed in statute miles per hour and T is the temperature in degrees Fahrenheit.

The formula to calculate a Celsius wind chill using V as the wind speed in kilometers per hour and T in degrees Celsius is:

T(wc) = 0.045(5.27V**0.5 + 10.45 - 0.28V) (T - 33) + 33

Note: In both formulas, ** means the following term is an exponent (i.e. 10**(0.5 ) means 10 to the 0.5 power, or the square root of V), - means to subtract, + means to add. The standard rules of algebra apply.

Note: When wind speeds are below 4 mph., the above formulas will give you a wind chill that is higher than the actual temperature. When wind velocities are near zero and you are standing still, your body heat warms the air near your body. This warm air near your body provides some insulation from the colder environment. As a result, it may actually feel warmer than the actual temperature.

Source for both formulas: The National Weather Service