Quick answer: At −10 °C with a 30 km/h wind, the wind chill is 13.12 + 0.6215×(−10) − 11.37×30^0.16 + 0.3965×(−10)×30^0.16 = −19.5 °C.
How it's calculated
The calculator uses the wind chill index adopted in 2001 by the US National Weather Service and Environment Canada: WCI = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965T·V^0.16, with T in °C and V the wind speed in km/h at 10 m. The °F version is 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T·V^0.16 with V in mph.
The index is a temperature: how cold calm air would have to be to cool your face as fast. It applies only at 10 °C (50 °F) or below and with wind of at least 4.8 km/h (3 mph).
Gulf winters rarely bring wind chill below freezing, but desert nights, mountain areas such as Abha, Taif and Jebel Jais, and travel to colder countries can. The risk bands are Environment Canada's frostbite guidance.
Worked examples
- −10 °C, 30 km/h: WCI = −19.5 °C
- 0 °F, 15 mph (NWS chart): WCT = −19 °F
- 5 °C, 20 km/h: WCI = 1.1 °C
Frequently asked questions
Does wind chill cool objects below the air temperature?
No. Wind makes skin and objects lose heat faster, but they cannot get colder than the air. A car radiator will not freeze at 2 °C however strong the wind.
Why is there no wind chill above 10 °C?
The formula was built for cold conditions. In warm weather, humidity matters more; use the heat index instead.
What wind speed should I use?
The wind speed from a weather report, which is measured at 10 m above the ground.
What is the wind chill at −10 °C and 30 km/h?
About −19.5 °C. On bare skin, that wind makes it feel nearly ten degrees colder than the thermometer says.
When does frostbite become a risk?
Environment Canada says exposed skin can freeze in 10 to 30 minutes once the wind chill reaches −28 to −39, and faster below that.
How do I protect myself in strong wind chill?
Cover your face, ears and hands, wear layers with a windproof shell on top, and stay dry. Wet clothes lose heat very quickly.