chill factor 
noun
A quantity expressing the perceived lowering of the air temperature caused by the wind.The freezer is - 40 deg F, and fans create a wind chill factor that drops the temperature to 100 degrees below zero....
- And the wind chill factor plus the cool temperatures, led to spot purchases of warm Disney Brand parkers at US $58 each.
- The cold moved slowly up the country towards Wellington yesterday, the wind chill factor keeping temperatures very low.