formula : one of OsczevskiBluestein or SiplePassel (see description); default is OsczevskiBluestein.

The convert([t, s], windchill, [ut, us]) function converts the temperature-speed pair $t,s$ to the corresponding windchill factor corresponding to the units of temperature ut.

The convert([t*Unit(ut), s*Unit(us)], windchill ) function is similar to the first calling sequence.

The formula used by the U.S. National Weather Service and Environment Canada is

where T is the temperature in degrees Fahrenheit, and V is the wind velocity in miles per hour.  The result is the apparent temperature in degrees Fahrenheit.

The above formula was developed in 2001 by the Joint Action Group for Temperature Indices (see Osczevski and Bluestein).

This calculation is intended as an approximation. It is used only for wind speeds between 4 mph ( $6\frac{\mathrm{km}}{h}$ ) and 50 mph ( $80\frac{\mathrm{km}}{h}$ ).

The above Osczevski-Bluestein formula replaces an earlier formula for windchill due to Siple and Passel:

in which the variables are defined as in the previous formula.

Windchill computations using the Siple-Passel formula are possible by adding the option formula=SiplePassel in the call to convert.

$\mathrm{convert}\left(\left[37\,10\right]\,\mathrm{windchill}\,\left[\mathrm{degF}\,\mathrm{mph}\right]\right)$

$29.92427177$

$\mathrm{convert}\left(\left[37\,10\right]\,\mathrm{windchill}\,\left[\mathrm{degF}\,\mathrm{mph}\right]\,\mathrm{formula}=\mathrm{SiplePassel}\right)$

$24.54590909$

$\mathrm{convert}\left(\left[3\,16\right]\,\mathrm{windchill}\,\left[\mathrm{degC}\,\frac{\mathrm{km}}{h}\right]\right)$

$\mathrm{-0.8629766}$

$\mathrm{convert}\left(\,\mathrm{temperature}\,\mathrm{degC}\,\mathrm{degF}\right)$

$30.4466421$

Osczevski, Randall, Maurice Bluestein, 2005: The New Wind Chill Equivalent Temperature Chart. Bulletin of the American Meteorological Society, 86, 1453–1458. doi: http://dx.doi.org/10.1175/BAMS-86-10-1453