Apparent temperature calculator
This tool combines the effect of humidity and wind into one number close to what you feel in the shade, hot or cold.
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Processing and privacy: The result is calculated inside your browser and your data is not sent to any server.
How to use it
- Enter air temperature, temperature unit, relative humidity, wind speed and speed unit.
- The result appears straight away and updates as you edit.
- Copy the result, or copy a link that keeps the same values to share it.
How it is calculated
AT = Ta + 0.33e − 0.70ws − 4.00, where e is vapour pressure in hPa = (RH ÷ 100) × 6.105 × exp(17.27Ta ÷ (237.7 + Ta)) and ws is wind speed in m/s.
Example
Inputs: Air temperature = 32, Temperature unit = Celsius (°C), Relative humidity = 50 %, Wind speed = 10, Speed unit = km/h. Result: Apparent temperature: 33.9 °C; In the other unit: 93 °F; Water vapour pressure: 23.69 hPa.
Limits and caveats
- This version leaves out sunshine, so it feels warmer in direct sun.
- Uses wind at 10 m height and can differ a little from the separate NWS heat and cold indices.
Questions about this tool
What does feels like mean in weather apps?
An estimate of what the body feels after humidity and wind; agencies calculate it in slightly different ways.
Why does wind lower the apparent temperature?
It carries heat away from the skin and speeds up sweat evaporation.
How is it different from the heat index?
The heat index uses only temperature and humidity; this formula adds wind and also works in the cold.