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Science

Wind Chill Calculator

When wind picks up, convection accelerates heat loss from your skin so the air feels colder than the thermometer says. The wind chill index combines air temperature and wind speed into a single "feels-like" temperature.

Feels-like temperature

Within the official validity range (air temp ≤ 10 °C and wind ≥ 4.8 km/h).

Frostbite risk (exposed skin)

Formula (2001 NWS / Environment Canada)

WC = 13.12 + 0.6215 T − 11.37 V^0.16 + 0.3965 T · V^0.16

T is air temperature (°C) and V is wind speed at 10 m (km/h). Cold air plus high wind accelerates heat loss — perceived temperature can be 5–15 °C lower than air temperature.

Formula

WC = 13.12 + 0.6215 T − 11.37 V^0.16 + 0.3965 T · V^0.16 (T = °C, V = km/h)

Frequently asked

How different is wind chill from the actual air temperature, and why does it feel so much colder?

Going from calm to a 30–50 km/h breeze typically drops the feels-like temperature by 5–15 °C. Your skin forms a thin layer of warmer air (a boundary layer) that wind strips away, accelerating convective heat loss; the colder and windier it is, the faster you lose heat. For example, −5 °C with a 30 km/h wind feels like ~−13 °C, and −15 °C with 50 km/h feels like ~−28 °C.

At what wind-chill temperature should I start worrying about frostbite?

Per Environment Canada: ≥ −10 °C no notable risk; −10 to −28 °C discomfort after hours; −28 to −40 °C frostbite possible after 10–30 min; −40 to −48 °C frostbite in 5–10 min; −48 to −55 °C frostbite in 2–5 min; below −55 °C extreme, frostbite in under 2 min. Even Hong Kong's coldest peaks rarely exceed the "low" band, but mainland Asia and northern climates routinely hit moderate or higher.

Can wind chill drop below absolute zero, or is there an upper / lower bound?

No. Wind chill is a *felt* temperature, not the actual air temperature — air does not get colder than its real value just because it is windy. A wind chill of −60 °C means your body loses heat at the same rate as it would in calm −60 °C air, not that the air itself is at −60 °C. Real-world values below −55 °C only show up in extreme polar weather.

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