WCI = 35.74 + 0.6215T – 35.75V (**0.16) + 0.4275TV(**0.16) where T is the air temperature in degrees Fahrenheit, V is the wind velocity in miles per hour. And ** stands for “to the power of” because the way this is traditionally written in mathematics does not correspond well to typed newspaper copy. This awkward-looking equation is the formula for the Wind Chill Index.

But the reality of “wind chill” is not nearly as precise as this equation looks. The fact is that different people respond differently to similar weather conditions. Further, sunshine is left out of the equation and so, too, is the fact that wind is officially measured at ten meters above the ground (33 feet) which is not where most of us encounter the wind.

Wind does not actually make the air colder; but it does whisk heat away from exposed skin, causing our bodies to lose heat.

The system is far from perfect, but it does at least offer a numerical guide for people to easily quantify the combined cooling effect of wind and cold.

Meteorologist John Wheeler