Wind Chill Calculator

What is wind chill?

Wind chill is the apparent temperature your skin experiences when cold air is moving. Stand still on a 0°F (−18°C) morning and you feel the actual cold. Add a 30 mph wind and the same air feels closer to −19°F. The thermometer hasn't changed; your skin is losing heat several times faster because the wind keeps stripping away the thin layer of warm air your body radiates outward.

The number matters for one reason: how fast your skin cools determines how quickly frostbite happens. A wind chill of −19°F can frostbite exposed skin within about 30 minutes. At −32°F, the window drops to 10 minutes. At −60°F — conditions that aren't unusual in parts of Alaska, the upper Midwest, or interior Canada — frostbite can set in within 5 minutes. The Wind Chill Calculator gives you both the apparent temperature and, when relevant, the rough time-to-frostbite for exposed skin.

If you've ever stepped outside on a windy winter day and felt your face go numb in a way the thermometer reading didn't predict, the wind chill explains it.

How to use the Wind Chill Calculator

Two inputs, instant result. Unit conversions are handled internally so you can pick whatever combination matches your local weather report.

1. Enter the air temperature. Pick °F or °C from the dropdown.
2. Enter the wind speed. Pick mph or km/h.
3. Read the "feels like" temperature in both scales.
4. If conditions are severe, a frostbite warning appears below the result with an estimate of how long exposed skin can stay safe.

The formula has a defined validity range: air temperature at or below 50°F (10°C), wind speed at or above 3 mph (about 5 km/h). Outside that range, wind chill isn't physically meaningful — above 50°F, the body's heat management is driven by sweating rather than convection, and below 3 mph the air around your skin isn't moving fast enough to matter. The calculator will tell you when your inputs land outside the valid range.

The formula behind the number

The current wind chill formula has been in use since 2001. It replaced a much older 1939 formula (Siple and Passel) that was based on measuring how fast water in a plastic cylinder froze in cold wind — a setup that didn't actually match human skin response. The NWS, in cooperation with Environment Canada, retired the old formula after running new tests with human subjects in cold-air wind tunnels, with skin-temperature sensors attached to the face.

The metric version, used by Environment Canada:

Both versions produce identical readings after unit conversion. The calculator uses the imperial formula internally and converts your inputs automatically.

Worked example: it's −10°C (14°F) with a 30 km/h wind — a fairly typical winter morning in Minneapolis, Toronto, or much of northern Europe.

• Convert: T = 14°F, V = 30 km/h ≈ 18.64 mph
• V^0.16 = 18.64^0.16 ≈ 1.562
• T_wc = 35.74 + 0.6215(14) − 35.75(1.562) + 0.4275(14)(1.562)
• T_wc = 35.74 + 8.70 − 55.84 + 9.35
• T_wc ≈ −2°F, or roughly −19°C

The thermometer says −10°C. Your skin reads −19°C. Nine degrees of difference — entirely from the wind stripping warm air off your face.

Frostbite time by wind chill

The NWS publishes time-to-frostbite estimates for exposed skin on healthy adults. The numbers below are averages — individual factors (dampness, prior cold exposure, smoking, age, circulation) can shift them by a factor of two in either direction.

The lowest wind chill ever recorded was around −116°F (−82°C) at Vostok Station in Antarctica during the 1980s. In settled-area weather records, interior Alaska has hit roughly −105°F (−76°C). The 2001 NWS chart tops out around −98°F because human-subject testing wasn't conducted below that — the formula will still produce a number, but its accuracy hasn't been validated at those extremes.

What changed in 2001

The old Siple-Passel formula from 1939 was derived from an unusual experiment: Paul Siple and Charles Passel hung plastic cylinders full of water in the Antarctic wind, measured how fast they froze, and built a formula around the data. The result was a wind chill table that turned out to be far more extreme than what humans actually felt.

At 0°F with a 30 mph wind, the old formula gave roughly −40°F. The 2001 formula gives about −19°F. Same conditions, dramatically different number. The difference matters because the old formula made winter weather sound more dangerous than it usually was, which led to two problems: people stopped trusting wind chill warnings, and the warnings stopped corresponding to actual frostbite risk.

The 2001 formula was developed by a joint US-Canadian team. They ran 12 human volunteers through walks on treadmills inside refrigerated wind tunnels, with thermocouples on their faces measuring skin temperature directly. The resulting model predicts the time it takes for facial skin to drop to a temperature where frostbite begins — a much more relevant metric than how fast water freezes in a plastic tube.

If you ever see a wind chill table that shows much more extreme numbers than your current weather app, it's likely using the old formula or computing from one of the in-between approximations that were briefly used in the 1980s and 90s. Stick with the 2001 NWS formula — it's what every reputable weather service uses today.

What wind chill doesn't tell you

A few important limits:

• Wind chill applies only to living skin. Your car's engine doesn't get colder than the air, no matter how hard the wind is blowing. Frozen pipes inside walls don't get colder either. Wind chill is a description of how fast warm objects lose heat to cold moving air — and only objects warmer than the air are losing heat. Cold inanimate objects sit at air temperature.
• Covered skin doesn't experience wind chill the way exposed skin does. Proper winter clothing — windproof outer shell, insulating mid-layer — reduces the wind chill effect to nearly zero on covered areas. Wind chill numbers describe risk to exposed face, neck, and hands, not to your torso under a parka.
• Dampness drastically worsens cold-skin response. Wet skin loses heat 25-30x faster than dry skin. The standard wind chill formula assumes dry skin. If you've been sweating heavily and stop in cold wind, frostbite risk climbs sharply faster than the formula suggests.
• Wind speed at "official" weather-station height is 10 meters above the ground. Wind speed at face height is usually 60-80% of that. Forecast wind chills are slightly more severe than what you'll actually feel at street level, unless you're in an open field or on a ridge.
• Calm-air cold can still cause frostbite. The formula gives nonsensical results below 3 mph wind, but that doesn't mean frostbite is impossible in still air. At very low temperatures (below about −30°F), exposed skin can freeze in minutes regardless of wind. Treat any extreme cold as serious, calm or not.

Wind chill vs. heat index vs. "feels like"

Two formulas, one umbrella term:

The two formulas don't overlap meaningfully. There's a wide moderate range (roughly 50-80°F) where neither produces a different number from the dry-bulb temperature, and "feels like" simply mirrors the thermometer reading.

Related calculations

Weather involves more than one number. Pair the wind chill with:

• Heat Index Calculator — the warm-weather counterpart. NWS Rothfusz formula with caution tiers from "Caution" to "Extreme Danger."
• Dew Point Calculator — the absolute-moisture measure used by meteorologists. Better than relative humidity for comparing comfort across different temperatures.
• Temperature Converter — quick °F ↔ °C ↔ K if your local forecast and your car's display disagree on units.

Frequently asked questions

Why doesn't wind chill matter for animals or inanimate objects?

Wind chill describes how fast warm objects lose heat to cold moving air. Most animals are warm and have skin or fur, so wind chill applies to them in roughly the same way it applies to humans — short-haired dogs in particular feel wind chill closely to how people do. Inanimate objects don't generate metabolic heat, so they cool to air temperature and stay there, wind or no wind. Your car battery's vulnerability to cold depends only on the air temperature.

At what temperature should I worry about frostbite?

NWS thresholds for healthy adults with dry, exposed skin: 30 minutes to frostbite at a wind chill of −19°F (−28°C), 10 minutes at −32°F (−36°C), 5 minutes at −60°F (−51°C). Children, elderly people, smokers, and anyone with circulation problems hit those thresholds faster. Cover exposed skin (face, ears, fingers) whenever wind chill drops below about 0°F — it's a small effort that prevents most cold-weather injuries.

Does wind chill affect how cold I feel inside a house?

Only if there's wind getting through. A drafty old house with poor weatherstripping can have indoor air movement fast enough to produce a small wind chill effect at the leaky spots — usually around windows and exterior doors. In a tight modern house, indoor wind speed is negligible and wind chill doesn't apply. If a room feels colder than the thermostat reads, you probably have a draft.

Can I get frostbite at 35°F?

Not from cold alone. The wind chill formula tops out at 50°F because the body's heat-regulation mode changes above that — you're not losing heat fast enough through convection for frostbite to be a risk. You can, however, get hypothermia at much warmer temperatures than people expect, especially if you're wet. Hypothermia is a core-temperature problem; frostbite is a skin-temperature problem. Different threats, different thresholds.

What's the wind chill at room temperature with a fan blowing?

None, in the wind-chill-formula sense. A fan moves room-temperature air across your skin, accelerating sweat evaporation and convective heat loss — which is why a fan feels cooling. But the formal wind chill formula doesn't apply because the air temperature is above 50°F. What you feel from a fan in summer is heat-index-style cooling: evaporative, not convective in the cold-skin sense.

Does wind chill make my heating bill higher?

Indirectly. If your house has air leaks, more wind pushes more outside air through them, raising the rate at which your furnace has to replace heat. The air inside your walls is still at the dry-bulb outside temperature, not the wind chill — your insulation's effectiveness depends on the actual air temperature, not the apparent one. But the volume of cold air infiltrating a leaky building scales with wind speed, so a windier day does cost more to heat in a non-airtight home.

Why do US and Canadian forecasts sometimes disagree on the wind chill number?

They shouldn't, but historically they did. From 2001 onward both countries use the same underlying formula (Environment Canada and NWS were co-authors), so converted numbers should match. Small discrepancies usually trace to different rounding conventions or to one source using the older pre-2001 formula. Modern weather services have all converged on the 2001 formula; if you see a meaningful disagreement, one source is probably out of date.