Wind Chill Calculator

What wind chill actually measures

Still air next to your skin warms up and forms an insulating layer. Wind strips that layer away and replaces it with cold air, so heat leaves faster. Wind chill expresses that rate of heat loss as the still-air temperature that would cool you equally fast. It applies to exposed human skin — it does not lower the temperature of your car, your pipes or a bucket of water.

The 2001 revision

The original 1945 formula came from measuring how fast water froze in plastic cylinders, and it overstated the effect substantially. The current formula, adopted by the US and Canada in 2001, came from trials with human volunteers in a chilled wind tunnel, uses wind speed at face height rather than at the standard 10-metre anemometer height, and assumes no sunlight. It is defined only at or below 50 °F with winds above 3 mph — outside that range the page says so instead of extrapolating.

Frostbite times are the practical output

At −5 °F with a 20 mph wind, the wind chill is about −29 °F and exposed skin can freeze in around 30 minutes. At −25 °F with the same wind it is roughly 10 minutes. Those times assume bare skin; covering it changes everything, which is the actual advice hiding inside the number.

Frequently Asked Questions