Feels Like Temperature (Wind Chill and Heat Index)
Enter the air temperature, with the wind speed for cold weather and the humidity for hot weather. The page uses the index that applies.
Wind chill applies at 10 °C or colder with wind of at least 4.8 km/h (3 mph). The heat index applies from 27 °C (80 °F). Between them, the air temperature is the best guide.
Worked examples
Cold and windy
-10 C with a 30 km/h wind
Feels like -19.5 C
Wind chill index.
Hot and humid
32.2 C (90 F) at 70% humidity
Feels like about 41 C (106 F)
Extreme caution band.
About Feels Like Temperature (Wind Chill and Heat Index)
Two indexes describe how the weather feels. In cold weather, wind carries heat away from exposed skin, so it feels colder than the thermometer says: this is wind chill. At minus 10 degrees Celsius with a 30 kilometre per hour wind it feels like about minus 20. In hot weather, humid air slows the evaporation of sweat, so the body cools less well and it feels hotter than the thermometer says: this is the heat index. At 32 degrees with 70% humidity it feels like about 41.
This calculator uses the standard formulas: the wind chill index agreed by the weather services of Canada, the USA and the UK, and the heat index regression from the US National Weather Service. It chooses the one that applies to your temperature and shows the warning band for frostbite or heat illness. These are guides for healthy adults. Wind does not cool objects below the air temperature, so it does not freeze water pipes or a car engine that would not freeze anyway.
How to use Feels Like Temperature (Wind Chill and Heat Index)
- Enter the air temperature and choose Celsius, Fahrenheit or kelvin.
- For cold weather, enter the wind speed in km/h, mph or m/s.
- For hot weather, enter the relative humidity.
- Read the feels like temperature and the risk band.
Common uses
- Dressing for a winter walk or a mountain trip
- Judging the risk of frostbite on exposed skin
- Checking the heat risk for outdoor work or sport
- Understanding weather forecasts that quote a feels like figure
Frequently asked questions
What is the wind chill formula?
13.12 + 0.6215 Ta - 11.37 V^0.16 + 0.3965 Ta V^0.16, with Ta in degrees Celsius and V in km/h at 10 metres. It applies at 10 degrees or colder and for wind of 4.8 km/h or more.
What is the heat index?
It combines air temperature and relative humidity into a single figure for how hot it feels, using a regression from the US National Weather Service. It applies at 27 degrees Celsius (80 Fahrenheit) and above.
Does sunshine change the result?
Yes, but not in these formulas. Direct sun can add up to about 8 degrees Celsius to how hot it feels, and sun makes it feel warmer in cold weather too.
Why is nothing shown at 15 degrees?
Between 10 and 27 degrees neither index is defined, because the effect of wind or humidity on how the weather feels is small. The air temperature is the best guide.