Here is how you calculate the New Wind Chill Index:

      T_wc 5 35.74 1 0.6215T – 35.75(V⁰.¹⁶) 1 0.4275T(V⁰.¹⁶)

T_wc is the wind chill in degrees F, V is the wind speed in miles per hour, and T is the temperature in degrees F.