Is the cooling effect of wind on exposed skin.
The formula to compute Wind Chill:

Wind chill temperature = 35.74 + 0.6215**T** - 35.75**V** (**0.16) + 0.4275**T****V**(**0.16)

Where **V** is the wind speed in statute miles per hour

**T** is the temperature in degrees Fahrenheit.

**Heat Index**
combines the effects of heat and humidity. When heat and humidity combine to reduce
the amount of evaporation of sweat from the body, outdoor exercise becomes dangerous even for those in good shape.

The formula to calculate Heat Index is

(1) Heat index(HI), or apparent temperature(AI) = -42.379 + 2.04901523(Tf) + 10.14333127(RH) - 0.22475541(Tf)(RH) -6.83783x10**(-3)*(Tf**(2)) - 5.481717x10**(-2)*(RH**(2)) + 1.22874x10**(-3)*(Tf**(2))*(RH) + 8.5282x10**(-4)*(Tf)*(RH**(2)) -1.99x10**(-6)*(Tf**(2))*(RH**(2))

Where Tf = air temperature in degrees Fahrenheit,

RH= relative humidity expressed as a whole number.