Calculate perceived outdoor temperature from air temperature and wind speed.
This tool provides estimates for informational purposes only. It is not a substitute for professional advice. Individual results vary based on your inputs and assumptions, so review important decisions with a qualified professional.
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Wind chill is the perceived decrease in air temperature felt by the human body due to the flow of cool air across exposed skin. While the thermometer may read 0°C (32°F), a strong wind can make it feel significantly colder — accelerating heat loss from exposed skin and dramatically increasing the risk of frostbite and hypothermia. Understanding wind chill is vital for outdoor workers, winter sports enthusiasts, parents, and anyone planning activities in cold weather across the UK, Canada, and northern United States.
The current internationally adopted wind chill formula was jointly developed by the US National Weather Service (NWS) and Environment and Climate Change Canada's Meteorological Service of Canada (MSC) in 2001. It replaced earlier formulas and is validated against human subject trials. The formula in Celsius:
WC = 13.12 + 0.6215T - 11.37V^0.16 + 0.3965T x V^0.16
Where T is air temperature in degrees Celsius and V is wind speed in km/h. The formula is valid for air temperatures at or below 10°C (50°F) and wind speeds above 4.8 km/h (3 mph). Below these thresholds, wind chill is not significantly different from air temperature.
In Fahrenheit: WC = 35.74 + 0.6215T - 35.75V^0.16 + 0.4275T x V^0.16, where T is in °F and V in mph.
| Air Temp (C) | 10 km/h wind | 20 km/h wind | 40 km/h wind | 60 km/h wind |
|---|---|---|---|---|
| 0 | -3 | -5 | -8 | -10 |
| -5 | -9 | -12 | -15 | -17 |
| -10 | -15 | -18 | -22 | -25 |
| -15 | -21 | -25 | -29 | -32 |
| -20 | -27 | -31 | -36 | -39 |
| -30 | -38 | -43 | -50 | -53 |
The 2001 NWS/MSC wind chill formula includes validated frostbite risk thresholds for exposed skin. Frostbite occurs when skin tissue freezes — first the outer skin layer (frostnip), then deeper tissue (superficial and deep frostbite):
| Wind Chill Value | Frostbite Time (exposed skin) | Risk Level |
|---|---|---|
| -10 to -24 C (14 to -11 F) | 30 minutes or less | Caution — frostbite possible |
| -25 to -34 C (-13 to -29 F) | 10–30 minutes | High risk |
| -35 to -59 C (-31 to -74 F) | 5–10 minutes | Very high risk |
| -60 C (-76 F) and below | Under 2 minutes | Extreme danger — limit all outdoor exposure |
These thresholds apply to exposed skin on a person walking at approximately 4.8 km/h (3 mph). Physical activity, wet skin, wet clothing, altitude, and individual physiology all affect actual frostbite onset time.
The UK Met Office includes wind chill in its winter weather forecasts and its Cold Health Alert system (operated jointly with the UK Health Security Agency). The UK uses the same 2001 NWS/MSC formula as North America. Met Office guidance specifically addresses:
While extreme wind chills of -30°C or below are rare in the UK lowlands, the Scottish Highlands regularly experience conditions where air temperatures of -10°C combined with 50+ km/h winds produce wind chills below -25°C. The highest summit weather stations in Scotland (Cairn Gorm at 1245m elevation) have recorded wind chills equivalent to -40°C in severe winter storms.
The National Weather Service issues official wind chill products based on regional thresholds that account for population acclimatisation differences:
Northern US states (Minnesota, Wisconsin, North Dakota, Montana) routinely experience wind chill values below -40°F during arctic outbreaks. The record low wind chill in the US was approximately -80°F (-62°C) in Montana. During the January 2019 polar vortex event, parts of the Midwest experienced wind chills of -50 to -60°F (-46 to -51°C), with frostbite possible in minutes and Chicago colder than parts of Antarctica.
Wind chill is specifically the cold-weather "feels like" temperature. Its warm-weather equivalent is the heat index. Note these important limitations of wind chill:
| Beaufort Scale | Description | km/h | mph | knots | m/s |
|---|---|---|---|---|---|
| 0 | Calm | <1 | <1 | <1 | <0.5 |
| 3 | Gentle breeze | 12–19 | 8–12 | 7–10 | 3.4–5.4 |
| 6 | Strong breeze | 39–49 | 25–31 | 22–27 | 10.8–13.8 |
| 8 | Gale | 62–74 | 39–46 | 34–40 | 17.2–20.7 |
| 10 | Storm | 89–102 | 55–63 | 48–55 | 24.5–28.4 |
| 12 | Hurricane | >118 | >73 | >64 | >32.7 |
The three-layer clothing system is the standard recommendation for managing wind chill in outdoor activities:
Critically, extremities (face, hands, ears, feet) are most vulnerable to wind chill and frostbite. The UK Mountain Rescue Council and US National Ski Areas Association both recommend covering all exposed skin when wind chill drops below -15°C (-5°F).
UK Health and Safety Executive (HSE) guidance under the Management of Health and Safety at Work Regulations 1999 requires employers to assess wind chill as an outdoor hazard. US OSHA has no specific wind chill regulation but enforces the General Duty Clause — employers must provide workplaces free from recognised hazards including cold stress. Key employer obligations:
Wind chill is the perceived drop in temperature caused by wind removing heat from exposed skin. The current NWS/MSC formula (2001): WC = 13.12 + 0.6215T - 11.37 x V^0.16 + 0.3965T x V^0.16, where T is air temperature in Celsius and V is wind speed in km/h. It is valid below 10°C and above 4.8 km/h wind speed.
Frostbite on exposed skin can begin within 30 minutes at wind chill values of -10 to -24°C. At -25 to -34°C, frostbite can occur in 10–30 minutes. At -35°C and below, frostbite can occur in under 10 minutes. Below -60°C, unprotected skin can freeze in under 2 minutes.
Wind chill only affects living things (humans and animals) with internal heat sources. It does not cool inanimate objects below the actual air temperature. A metal pipe cannot freeze at -8°C wind chill when air temperature is 0°C — only the human skin feels -8°C. However, wind does increase evaporation and can cool objects to the actual air temperature faster than in calm conditions.
The NWS issues a Wind Chill Warning when wind chill values are expected to reach -30°F (-34°C) or below for 3+ hours in most areas. In some northern regions, warnings are issued at -25°F (-32°C). A Wind Chill Advisory is issued for -20°F (-29°C) to -29°F (-34°C). These thresholds vary by region based on local acclimatisation.
The Met Office includes wind chill in mountain area forecasts and Cold Health Alerts. It uses the same 2001 NWS/MSC formula and reports wind chill as a "feels like" temperature. Mountain forecasts for areas like the Scottish Highlands include wind chill warnings due to the combination of sub-zero temperatures and high winds at altitude.
UK HSE guidance recommends enhanced controls when wind chill drops below -10°C (14°F), including warm rest facilities and increased break frequency. At -20°C wind chill (-4°F), only essential outdoor work should continue with maximum protection measures. US OSHA enforces the General Duty Clause requiring employers to protect against cold stress hazards at any dangerously cold wind chill value.
Use the three-layer clothing system: moisture-wicking base layer, insulating mid layer, and windproof/waterproof outer shell. Cover all exposed skin (face, neck, ears, hands). Gloves and a balaclava are essential below -15°C wind chill. Stay dry — wet clothing loses 90% of insulating value. Recognise early symptoms of frostbite (numbness, whiteness) and hypothermia (shivering, confusion).
Wind chill specifically refers to the cooling effect of cold wind on exposed human skin. "Feels like" or "apparent temperature" is a broader term that can include wind chill in cold weather or heat index in hot weather. Some weather services combine both effects (including solar radiation, humidity, and wind) into a single "apparent temperature" or "real feel" index that covers the full temperature range.