Wind Chill Calculator — how cold the wind makes it feel

How it works

Wind chill is the cold-weather counterpart of the heat index: it expresses how cold the air feels once wind is taken into account. Still air lets your body warm a thin insulating layer next to the skin; wind blows that layer away and speeds up heat loss, so a windy 0 °F feels far colder than a calm 0 °F.

This calculator uses the National Weather Service 2001 wind-chill formula:

WC = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16

where T is the air temperature in °F and V is the wind speed in mph. The formula applies for temperatures at or below 50 °F and winds of at least 3 mph; outside that range wind chill is not defined and the result is left blank.

Worked example

At 0 °F with a 15 mph wind, the wind chill is about −19.4 °F — nearly 20 degrees colder than the thermometer. Wind matters a lot: 10 °F with a 25 mph wind feels like −10.7 °F, while a milder 40 °F with 10 mph feels like 33.6 °F. The stronger the wind, the greater the chill at any given temperature.

Frequently asked questions

What is wind chill?

Wind chill is the apparent ("feels like") temperature in cold weather, combining the air temperature with the wind speed. Wind accelerates the loss of body heat, so a windy day feels colder than a calm one at the same temperature.

How is wind chill calculated?

The National Weather Service uses its 2001 formula, WC = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16, with temperature in °F and wind speed in mph. It was derived from heat-transfer models of the human face and replaced an older 1945 formula.

Why does wind make it feel colder?

Your body warms a thin layer of air right against your skin. Wind constantly blows that warmed layer away and replaces it with cold air, so heat escapes faster. The air temperature itself does not change — only the rate at which you lose heat does.

When does wind chill apply?

The formula is used for temperatures at or below 50 °F and wind speeds of at least 3 mph. Above 50 °F wind has little chilling effect, and below about 3 mph the air is nearly still, so wind chill is not reported outside that range.

Can wind chill cause frostbite?

Yes. Wind chill indicates how quickly exposed skin loses heat, and low values mean frostbite can set in fast — at a wind chill around −19 °F, frostbite is possible on exposed skin within about 30 minutes. The colder the wind chill, the shorter that time.

What is the difference between wind chill and heat index?

Both are apparent temperatures, but for opposite conditions. Wind chill applies in cold weather and depends on wind; the [heat index](heat-index-calculator) applies in hot weather and depends on humidity. Weather apps usually show whichever fits the current temperature.