Although the weather forecast give you a good idea of just how cold it's going to be on that slope, the actual air temperature is not the whole story: when you are outside; a flow of air will remove heat from you and the perceived temperature will be lower than the measured one.
The result is that you feel much colder when there is a wind, and this table will give you some idea just how much!
This drop in perceived temperature is known as the 'wind-chill factor', so for all you slope soarers, here's a little table that will tell you how cold it feels when the wind-chill factor is taken into account.
The left hand column is the actual air temperature, so find the correct one then follow the row across until you are under the wind speed. The temperature shown there is the perceived temperature caused by heat loss due to the wind.
|Wind-chill Factor Table (in Fahrenheit)|
|AIR TEMP||Wind speed in mph.|