The wind chill tables are based on the
rate of heat loss from a one liter cylinder of water at 33 C (91.4 F).
The tables are for this notional cylinder at various ambient
temperatures and velocities.

        WCI = (33 - t )*(10.45 - V + 10*sqrt(V))  kcal/m2/h

        where t = ambient temperature in C
              V = wind velocity in m/sec
              WCI = the "wind chill index"

        T = -0.04544*WCI + 33

        where T = the equivalent wind chill temperature

Conversion to degress F and miles per hour is left as an exercise for
the reader.  :)