“It’s 20°F but feels like 6°F” is a familiar winter forecast phrase — and it’s not marketing exaggeration, it’s a specific, well-defined calculation. Our wind chill calculator uses the same formula meteorologists rely on.
The formula
WCT = 35.74 + 0.6215T − 35.75(V^0.16) + 0.4275T(V^0.16)Where T is air temperature in °F and V is wind speed in mph. This is the official U.S. National Weather Service wind chill formula, adopted in 2001 to replace an older, less accurate model.
Example
20°F air temperature with 15 mph wind: 6.2°F feels-like temperature — an over 13-degree difference from the actual thermometer reading, purely from wind’s effect on heat loss.
Why wind makes cold feel colder
Your body constantly warms a thin layer of air right next to your skin. Wind strips that warmed layer away faster than your body can replace it, accelerating heat loss through convection. The stronger the wind, the faster this insulating air layer gets displaced — which is why wind chill drops quickly as wind speed increases, even without the actual air temperature changing at all.
When the formula doesn’t apply
The NWS formula is only valid for temperatures at or below 50°F and wind speeds of 3 mph or higher. Below that wind threshold, there isn’t enough airflow to meaningfully accelerate heat loss, and above 50°F, wind chill isn’t a meaningful safety concern — the calculator shows the actual air temperature in those cases instead of applying the formula out of its valid range.
Not the same as the actual temperature
A thermometer always reads the true air temperature regardless of wind. Wind chill describes how quickly exposed skin loses heat — and therefore how cold conditions feel and how much frostbite risk increases — not a literal change in the air’s physical temperature.