The wind does not cool the air, it cools you
Calculates the wind chill temperature from the air temperature and wind speed, and how quickly exposed skin is at risk.
A thermometer in the wind reads the same as one in still air. What changes is you: still air lets a thin warm layer form against your skin, and wind strips it away as fast as your body makes it.
The standard formula turns that into a single number — the temperature at which still air would take heat from you at the same rate. It applies to bare skin at ten degrees and below.
What this calculator shows
- The wind chill temperature and how far it is below the air temperature
- The wind speed in both metres per second and kilometres per hour
- How fast exposed skin is at risk of frostbite
What to keep in mind
- The North American formula is used, defined for air at 10 °C and below and winds above 4.8 km/h.
- It describes exposed skin. Under clothing the effect is far smaller, which is why the figure is a warning for face and hands rather than for the whole body.
FAQs
Does wind chill affect a car or a pipe?
No. Wind makes objects cool faster to the air temperature, but it cannot take them below it. Only something generating its own heat — a body — feels a wind chill.
When does frostbite become a real risk?
Around −28 °C of wind chill it takes about half an hour of exposure, at −38 about ten minutes, and below −48 a few minutes are enough.
Why does the formula stop at 10 °C?
Above that the body loses heat mainly by evaporation rather than convection, and the model no longer describes anything real. In warm air the heat index is the relevant figure.
Does it work at very high wind speeds?
It flattens out. Past about fifteen metres a second the boundary layer is already gone, so more wind takes little further off the effective temperature.
Worked example
Minus ten with a light wind
Input: −10 °C, 5 m/s
Output: feels like −17.4 °C
Note: Five metres a second is 18 km/h — a wind that barely moves branches. It still takes more than seven degrees off what the skin experiences.