If you've ever stood outside on a cold windy day, you know that the wind can make you feel much colder than the air temperature might indicate. The reason is that the wind blows away the thin layer of warm air that normally surrounds your body. Clothing acts as insulation to help trap this warm air, which is heated by your skin. The stronger the wind and the lower the temperature, the more rapidly you lose body heat.
Wind chill is the meteorological index that combines the effects of wind speed and temperature.
The wind makes you feel colder for two reasons. First, it blows away a thin layer of warm air that normally surrounds your body. Second, it draws away heat by quickly evaporating any moisture that forms on your skin. That's why you feel chilled when you step out of the shower. The stronger the wind, the greater the evaporation and the colder you feel.