Feels-like temperature
Enter the temperature, wind speed and humidity. The calculator picks the right index for the conditions, the same way the US National Weather Service builds its apparent temperature forecasts, and tells you why.
Feels like · Wind chill
21°F
−6°C · air 30°F
At 50°F or colder with a breeze, the wind is what you feel, so the NWS uses wind chill.
- Wind chill: 21°F
- Heat index: only used above 80°F
Boundaries: wind chill at 50°F (10°C) and below, heat index above 80°F (26.7°C). The marker shows your air temperature.
Weather safety: a calculation, not a forecast. Feels-like numbers do not account for sunshine, rain or what you are wearing; check your weather service's warnings before heading out.
How the calculator decides
“Feels like” is not one formula but a choice between two. The NWS defines its apparent temperature like this: when the temperature is 50°F (10°C) or lower, use the wind chill; when it rises above 80°F (26.7°C), use the heat index; in between, use the air temperature as it is. The calculator follows the same rule.
There is one extra case. Wind chill is only defined for winds above 3 mph (4.8 km/h), so on a calm, cold day the feels-like value is simply the air temperature. Both indices are shown under the result so you can see what each would say.
What the number leaves out
Each index was built for particular conditions. The heat index assumes shade and a light wind, and the NWS says full sun can add up to 15°F (8°C). The wind chill assumes a clear night sky with no warming from the sun. Neither knows about rain, how active you are or your clothes, so use the result as a guide alongside the forecast.
Sources
- National Weather Service. National Digital Forecast Database definitions (apparent temperature).
- National Weather Service. Wind Chill Chart and FAQ.
- National Weather Service. Wind Chill (assumptions of the 2001 index).
- NOAA Weather Prediction Center. The Heat Index Equation.
- National Weather Service. Heat index chart and safety.
Questions
Why does a weather app show a different feels-like number?
Weather services and apps do not all use the same method, and some also factor in sunshine. This page follows the NWS rules only, so compare it with the NWS forecast for your area.
Why is there a jump at 80°F?
Below the line the NWS uses the air temperature; above it, the heat index, which in very humid air is already a few degrees higher. The change is a rule, not a sudden change in the weather.
Does humidity matter in the cold?
Not in this calculation. Wind chill uses only temperature and wind, so humidity only comes into play above 80°F (26.7°C).