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Heat Index & Wind Chill Calculator: Feels-Like Temp

Enter the temperature in °F with humidity or wind speed in mph to get the National Weather Service heat index or wind chill and its risk level.

Tool inputs stay in your browser · optional AI search sends your query

Good to know: Scope: the “feels like” temperature for one moment outdoors, using National Weather Service formulas in °F and mph. Heat index: the NWS Weather Prediction Center method (a simple formula first, then the Rothfusz regression with its dry-air and humid-air adjustments when the result is 80°F or more) and the NWS heat risk levels (Caution 80–90°F, Extreme Caution 90–103°F, Danger 103–124°F, Extreme Danger 125°F+). This tool works out the heat index above 50°F. Heat index values are for the shade; NWS says direct sun can add up to 15°F. Wind chill: the NWS formula, which NWS defines only at or below 50°F with wind above 3 mph. Not included: Celsius and km/h, forecasts or live weather, dew point, the WBGT used for sports and work, frostbite time tables, and medical advice. Everything stays in this browser tab; nothing is sent or saved. Independent ToolsKo estimate, not an NWS product. Sources reviewed November 12, 2026.

How to use it (step by step)

  1. 1Choose “Feels-like (pick for me)”, or pick heat index for hot, humid days or wind chill for cold, windy days.
  2. 2Type the air temperature in °F. For heat index add the relative humidity (%), for wind chill add the wind speed in mph — your weather app shows both.
  3. 3Read the feels-like temperature and the NWS risk level, then plan: shade, water and breaks in the heat; layers and covered skin in the cold.

Words to know

Heat index
How hot it feels when humidity is added to the air temperature. Damp air slows sweat from drying, so your body cools down less.
Wind chill
How cold it feels on bare skin when wind blows heat away from your body. It is not the real air temperature.
Relative humidity (%)
How much water vapor is in the air compared with the most it can hold at that temperature. 100% means the air is full; 20% is very dry.
Frostbite
Skin and the tissue under it freezing in very cold, windy weather. Cover bare skin when the wind chill is very low.

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Sources & methods

References checked November 11, 2026. Read each tool’s scope and assumptions before relying on its result.

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