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Wind Chill Calculator

Computes the wind chill temperature from air temperature and wind speed with the 2001 JAG/TI formula used by the US National Weather Service and Environment Canada, and reports the frostbite risk band for exposed skin.

When to use

You need the 'feels like' temperature in cold windy weather, or how quickly exposed skin can freeze, for temperatures at or below 10 °C (50 °F) and winds of at least 4.8 km/h (3 mph).

Do not use when: The temperature is above 10 °C (50 °F) or the wind is below 4.8 km/h (the formula is undefined there); for hot humid weather use heat-index.

Formula

WC(°C) = 13.12 + 0.6215·T − 11.37·V^0.16 + 0.3965·T·V^0.16 with T in °C and V in km/h (identical to the NWS form WC(°F) = 35.74 + 0.6215·T − 35.75·V^0.16 + 0.4275·T·V^0.16 with T in °F, V in mph); defined for T ≤ 10 °C and V ≥ 4.8 km/h

The 2001 Joint Action Group for Temperature Indices formula models heat loss from a bare face walking at 4.8 km/h into the wind, with wind measured at 10 m. Frostbite bands: −28 to −39 °C skin freezes in 10–30 min, −40 to −47 in 5–10 min, −48 to −54 in 2–5 min, −55 and colder in under 2 min.

Inputs

Parameter	Type	Required	Description
`temperature`	number	yes	Air temperature in temperature_unit; must be at or below 10 °C (50 °F). Range: ≥ -100, ≤ 60
`temperature_unit`	enum: c \| f	default c	Unit of the temperature input(s).
`wind_speed`	number	yes	Wind speed measured at 10 m (standard anemometer height), in wind_speed_unit; must be at least 4.8 km/h (3 mph). Range: ≥ 0, ≤ 400
`wind_speed_unit`	enum: kmh \| mph \| ms \| knots	default kmh	Unit of the wind speed input.

Outputs

Output	Type	Unit	Description
`wind_chill_c`	number	°C	Wind chill temperature in Celsius.
`wind_chill_f`	number	°F	Wind chill temperature in Fahrenheit.
`temperature_c`	number	°C	Input temperature in Celsius.
`wind_speed_kmh`	number	km/h	Input wind speed in km/h.
`frostbite_risk`	string		Environment Canada risk band for the wind chill value.
`frostbite_time`	string		Freezing time for exposed skin from the Environment Canada table (bands start at −28 °C).

Example

−10 °C, 30 km/h: {"temperature":-10,"temperature_unit":"c","wind_speed":30,"wind_speed_unit":"kmh"} → {"wind_chill_c":-19.5,"wind_chill_f":-3.1,"wind_speed_kmh":30,"frostbite_risk":"Moderate risk (−10 to −27 °C)"}

5 °F, 25 mph: {"temperature":5,"temperature_unit":"f","wind_speed":25,"wind_speed_unit":"mph"} → {"wind_chill_f":-17.5,"wind_chill_c":-27.5,"temperature_c":-15,"wind_speed_kmh":40.2}

GET https://tttkmbb.com/api/v1/calculate/wind-chill?temperature=-10&temperature_unit=c&wind_speed=30&wind_speed_unit=kmh

Machine access

API: GET https://tttkmbb.com/api/v1/calculate/wind-chill (query parameters) or POST with a JSON body {"inputs": {...}}
Schema: https://tttkmbb.com/api/v1/calculators/wind-chill · Markdown: https://tttkmbb.com/weather/wind-chill.md · JSON definition: https://tttkmbb.com/weather/wind-chill.json
MCP: server https://tttkmbb.com/mcp, tool run_calculator with calculator_id="wind-chill"
OpenAPI operationId: calculate_wind_chill
Freshness: static. Authentication: none. Rate limit: fair use (see rate limits).

Sources

NWS – Wind Chill Chart (2001 JAG/TI formula) (government)
Environment and Climate Change Canada – Wind chill and the Wind Chill Index (frostbite risk table) (government)

FAQ

Why is there no result for light winds or mild temperatures?

The formula is only defined for air temperatures at or below 10 °C (50 °F) and winds of at least 4.8 km/h (3 mph); outside that range the calculator returns an error rather than a misleading number.

Is the wind measured at face height?

No. The formula expects the standard 10 m anemometer wind; it internally converts to face-level wind (about 2/3 of the 10 m value).

Does wind chill lower the temperature of objects?

No. It expresses the rate of heat loss from skin; a car radiator or pipe never cools below the actual air temperature.

Related calculators

Heat Index Calculator — The hot-weather counterpart.
Speed Converter — Convert wind speeds between km/h, mph, m/s and knots.
Temperature Converter — Plain °C ↔ °F conversion.