Wind Chill Calculator
Find the wind chill from air temperature and wind speed with the official NWS and Environment Canada formula, plus your frostbite risk and a full chart.
Feels about 19 °F colder than the 10 °F air in a 20 mph wind.
Six ECCC risk bands, from low on the left to extreme on the right. Ticks mark wind chills of −10, −28, −40, −48 and −55 °C (14, −18, −40, −54 and −67 °F).
Frostbite risk and what to do
Frostbite and hypothermia are possible if you stay outside for long periods without adequate protection.
- Wear a hat, a scarf or knit mask over your face and mouth, mittens or gloves, a water resistant coat and boots, and several loose layers (CDC).
- Keep the nose, ears, cheeks, chin, fingers and toes covered; frostbite most often affects these areas (CDC).
- Stay dry and get out of the wind when you can; wet clothing chills the body rapidly (ECCC).
Frostbite signs (CDC): redness or pain first, then a white or grayish yellow patch, skin that feels firm or waxy, and numbness. Hypothermia signs: shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech and drowsiness. A body temperature below 95 °F needs medical care right away.
Your calculation
The same steps the calculator runs, with your numbers.
- Limits: 10 °F ≤ 50 °F and 20 mph > 3 mph, so the formula applies.
- V^0.16 = 20^0.16 = 1.6150.
- 0.6215 × T = 0.6215 × 10 = 6.2150.
- 35.75 × V^0.16 = 35.75 × 1.6150 = 57.7352.
- 0.4275 × T × V^0.16 = 0.4275 × 10 × 1.6150 = 6.9040.
- Wind chill = 35.74 + 6.2150 − 57.7352 + 6.9040 = −8.88 °F, rounded to −9 °F.
- Risk: (−8.88 − 32) × 5 ÷ 9 = −22.71 °C, rounded to −23, in the ECCC moderate band.
Wind chill chart
Wind chill in °F by air temperature (columns, °F) and wind speed (rows, mph). The outlined cell is the nearest to your inputs.
High: 10 to 30 minVery high: 5 to 10 minSevere: 2 to 5 minExtreme: under 2 minUnshaded: low or moderate
Wind chill estimates how cold exposed skin feels and is not a diagnosis. Follow your local weather service alerts and seek medical care for suspected frostbite or hypothermia.
What Is Wind Chill?
Wind chill is how cold the air feels on exposed skin once the wind is added to the actual temperature. The National Weather Service (NWS) bases it on the rate of heat loss from skin caused by wind and cold: as the wind increases, it draws heat from the body, driving down skin temperature and eventually internal body temperature. This wind chill calculator uses the same index as the NWS and Environment and Climate Change Canada (ECCC), so its results match the forecasts and charts both agencies publish.
In winter, wind chill is the feels like temperature. ECCC explains it with an example: if the air is −10 °C and the wind chill is −20, your face feels as cold in the wind as it would on a calm day at −20 °C. The index is written in temperature units, but no thermometer can measure it. It describes a sensation and a rate of heat loss.
On a calm day your body warms a thin layer of air next to the skin. Wind strips that layer away and dries moisture from the skin, so you lose heat faster and your body has to keep warming new air. Wet skin chills even faster because there is more moisture to evaporate.
Wind chill applies only to people and animals. Wind cools a car, a pipe or a roof faster, but none of them can fall below the actual air temperature.
Wind Chill Formula in Fahrenheit and Celsius
The current wind chill formula took effect in the United States on November 1, 2001, after the Meteorological Service of Canada adopted it in October 2001. It came from the Joint Action Group for Temperature Indices (JAG/TI), a group of US and Canadian agencies chaired by the NWS. Both countries use one equation, written once for °F and mph and once for °C and km/h.
The formula is defined only for air temperatures at or below 50 °F (10 °C) and wind speeds above 3 mph (about 4.8 km/h). Outside that range the calculator shows the air temperature with an explanation instead of a wind chill. ECCC reports wind chill in forecasts only when the temperature is 0 °C or below and the wind is 5 km/h or more, because there is no frostbite risk above freezing.
The two versions agree. Converting −10 °C and 30 km/h to 14 °F and 18.64 mph gives −3.09 °F, which is −19.49 °C, against −19.52 °C from the metric formula. Across the full NWS chart the two equations never differ by more than 0.06 °C. The calculator keeps full precision through every step and rounds only the final value, which is why the steps show −8.88 before the rounded −9.
How to Calculate Wind Chill Manually
- Check the limits. The air must be 50 °F (10 °C) or colder and the wind faster than 3 mph (4.8 km/h).
- Use the forecast wind. Forecasts and station reports give wind at 33 feet (10 meters), which is what the formula expects.
- Convert units if needed. Multiply knots by 1.852 or meters per second by 3.6 to get km/h, and divide km/h by 1.609344 to get mph.
- Raise the wind speed to the power 0.16. On a phone calculator, enter the speed, press x^y, then enter 0.16.
- Add the four terms, keeping the signs, then round the result to a whole degree.
Take 0 °F with a 15 mph wind, the example the NWS uses. First, 15^0.16 = 1.5423. Both temperature terms are zero, so WC = 35.74 − 35.75 × 1.5423 = 35.74 − 55.1380 = −19.40, which rounds to −19 °F, the same value the NWS chart shows. Converted, −19.40 °F is −28.55 °C, inside the ECCC high band, and the NWS notes that exposed skin can freeze in 30 minutes at this wind chill.
A colder case shows how fast the numbers fall. For −20 °F and a 30 mph wind, 30^0.16 = 1.7232, then 35.74 − 12.4300 − 61.6049 − 14.7335 = −53.03 °F, rounded to −53 °F. That is −47.24 °C, in the ECCC very high band, where exposed skin can freeze in 5 to 10 minutes.
Wind Chill Chart in °F and °C
This wind chill chart lists rounded results for common conditions, computed with the formulas above. Every value matches the published NWS and ECCC charts. Find the air temperature across the top and the wind speed down the side. Shaded cells fall in the ECCC high band or colder.
Wind chill chart, °F (wind in mph)
| mph | 40° | 30° | 20° | 10° | 0° | −10° | −20° | −30° | −40° |
|---|---|---|---|---|---|---|---|---|---|
| 5 | 36 | 25 | 13 | 1 | −11 | −22 | −34 | −46 | −57 |
| 10 | 34 | 21 | 9 | −4 | −16 | −28 | −41 | −53 | −66 |
| 15 | 32 | 19 | 6 | −7 | −19 | −32 | −45 | −58 | −71 |
| 20 | 30 | 17 | 4 | −9 | −22 | −35 | −48 | −61 | −74 |
| 25 | 29 | 16 | 3 | −11 | −24 | −37 | −51 | −64 | −78 |
| 30 | 28 | 15 | 1 | −12 | −26 | −39 | −53 | −67 | −80 |
| 40 | 27 | 13 | −1 | −15 | −29 | −43 | −57 | −71 | −84 |
| 50 | 26 | 12 | −3 | −17 | −31 | −45 | −60 | −74 | −88 |
| 60 | 25 | 10 | −4 | −19 | −33 | −48 | −62 | −76 | −91 |
Wind chill chart, °C (wind in km/h)
| km/h | 5° | 0° | −5° | −10° | −15° | −20° | −25° | −30° | −35° | −40° |
|---|---|---|---|---|---|---|---|---|---|---|
| 10 | 3 | −3 | −9 | −15 | −21 | −27 | −33 | −39 | −45 | −51 |
| 20 | 1 | −5 | −12 | −18 | −24 | −30 | −37 | −43 | −49 | −56 |
| 30 | 0 | −6 | −13 | −20 | −26 | −33 | −39 | −46 | −52 | −59 |
| 40 | −1 | −7 | −14 | −21 | −27 | −34 | −41 | −48 | −54 | −61 |
| 50 | −1 | −8 | −15 | −22 | −29 | −35 | −42 | −49 | −56 | −63 |
| 60 | −2 | −9 | −16 | −23 | −30 | −36 | −43 | −50 | −57 | −64 |
HighVery highSevereExtremeUnshaded: low or moderate
The calculator builds the full chart, from 40 °F to −45 °F and 5 to 60 mph, or from 5 °C to −50 °C and 5 to 80 km/h, and outlines the cell nearest your inputs.
Frostbite Time and Wind Chill Risk Categories
ECCC groups wind chill values into six risk bands and gives the time it takes exposed skin to freeze in each. The calculator uses these bands for the risk chip, the scale bar and the frostbite time. It converts the wind chill to °C and rounds it to a whole number before choosing the band.
| Risk | Wind chill (°C) | About (°F) | Exposed skin can freeze |
|---|---|---|---|
| Low | 0 to −9 | 32 to 16 | Unlikely; slight discomfort |
| Moderate | −10 to −27 | 14 to −17 | During long exposure without protection |
| High | −28 to −39 | −18 to −38 | 10 to 30 minutes |
| Very high | −40 to −47 | −40 to −53 | 5 to 10 minutes |
| Severe | −48 to −54 | −54 to −65 | 2 to 5 minutes |
| Extreme | −55 or colder | −67 or colder | Under 2 minutes |
The freezing times come from a time dependent model of the human face built by Defence Research and Development Canada for the JAG/TI work. According to the federal report on the index, they describe the most susceptible 5 percent of people under a clear night sky, so most people have more time. Children, older adults and people with circulation problems are more susceptible, and in calm air at the same value frostbite develops more slowly than in wind.
When Is Wind Chill Dangerous?
ECCC says the risk of frostbite increases rapidly once the wind chill drops below −27 on the Celsius scale, about −17 °F. Danger also depends on how long you stay out, how much skin is exposed, whether you are wet and how active you are.
Cold weather advisories and extreme cold warnings
NWS criteria are set locally by each forecast office. In the NWS example for the Rochester, New York area, an Extreme Cold Warning is issued when the apparent temperature, with or without wind, is expected to fall to −25 °F or lower, and a Cold Weather Advisory covers air temperatures or wind chills from −15 °F to −24 °F. Thresholds elsewhere can be warmer or colder. ECCC does not issue wind chill warnings; it issues cold warnings that include wind chill, with thresholds that differ by region.
Signs of frostbite and hypothermia
- Frostbite: redness or pain may come first, then a white or grayish yellow patch, skin that feels unusually firm or waxy, and numbness. It most often affects the nose, ears, cheeks, chin, fingers and toes.
- Hypothermia in adults: shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech and drowsiness. Babies may have bright red, cold skin and very low energy.
- Emergency: a body temperature below 95 °F needs medical attention immediately.
The CDC advises getting a person with frostbite into a warm room, removing wet clothing and placing affected areas in water that is warm to the touch. Do not rub or massage frostbitten skin, do not walk on frostbitten feet or toes unless necessary, and do not warm the skin with a fireplace, heat lamp, radiator, stove, heating pad or electric blanket, because numb skin can be injured without the person feeling it.
Cars, Pipes and Pets
Wind chill does not apply to objects. In the NWS example, at −5 °F with a wind chill of −31 °F, a car radiator cools faster in the wind but stops at −5 °F. The same holds for water pipes and batteries, so protect them based on the air temperature.
Pets do feel the cold. The American Veterinary Medical Association (AVMA) says cats and dogs are susceptible to frostbite and hypothermia, should generally be kept inside in cold weather, and should never be left outside for long periods in below freezing weather. Small dogs, thin or short coated dogs and very young or very old dogs have a harder time, and ear tips and paws can freeze.
Wind Chill vs Heat Index
Wind chill and the heat index are both feels like temperatures, but they cover opposite weather. Wind chill uses temperature and wind for air at or below 50 °F. The NWS heat index uses temperature and relative humidity for hot weather: 96 °F at 65 percent humidity feels like 121 °F. Use the Heat Index Calculator for summer conditions.
Humidity is not part of wind chill. When the NWS tested the new index on 12 volunteers, relative humidity changed the result by less than 1 degree, so it was left out. Sunshine is also excluded: the index assumes a clear night sky, and bright sun can raise the wind chill by 10 °F to 18 °F.
Old vs New Wind Chill Formula
The first wind chill index came from Antarctic explorer Paul Siple, who coined the term, and Charles Passel. In the 1940s they timed how long water in plastic cylinders took to freeze at different temperatures and winds. Their 1945 index served the NWS and the Meteorological Service of Canada until 2001. A federal review later found that the old curve was never meant to be used above a 50 mph wind and that the experiment ignored the insulating effect of the container.
The 2001 index replaced the water cylinder with a model of the human face and modern heat transfer theory. It was checked in a chilled wind tunnel in Toronto, where the faces of six men and six women were exposed to a range of temperatures and winds. It also lowered the calm wind threshold from 4 mph to 3 mph, uses a consistent value for skin tissue resistance and assumes no warming from the sun. Charts printed before 2001 use the old index, so their values do not match this calculator.
Why the wind is measured at 33 feet
Weather stations mount anemometers at the national standard height of 33 feet (10 meters). Wind is slower near the ground, so the formula converts the 33 foot reading to an average adult face height of 5 feet inside the equation. Enter the forecast or station wind, not a reading taken at face level. The federal report on the index says a face level wind should be multiplied by 1.5 first: 10 mph at face level becomes 15 mph, which at 10 °F gives −7 °F instead of −4 °F.
How to Use the Calculator
- Units. Choose °F and mph or °C and km/h. The wind menu also takes m/s and knots and converts them first.
- Air temperature. The shaded air temperature from your forecast. Tap ± for values below zero.
- Wind speed. The sustained forecast wind. Enter 0 for calm air.
- Results. Wind chill, risk band and frostbite time, Beaufort force, the air temperature at which this wind reaches high risk, every step and the full chart.
Common Mistakes
- Entering a gust. Use the sustained wind speed; ECCC frostbite guidance refers to sustained winds.
- Measuring at face level. Multiply a handheld reading by 1.5.
- Mixing up knots and mph. 20 knots is 23 mph.
- Using it above 50 °F or for objects. Neither is covered by the index.
- Applying it unchanged to children. NWS tests used adults, so be more cautious with children, older adults and people in poor health.
Frequently Asked Questions
How do you calculate wind chill?
Use the National Weather Service formula: wind chill (°F) = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16, where T is the air temperature in °F and V is the wind speed in mph measured at 33 feet. Raise the wind speed to the power 0.16 first, then work out each term and add them. For 10 °F and 20 mph, 20^0.16 = 1.6150, so 35.74 + 6.2150 − 57.7352 + 6.9040 = −8.88, which rounds to −9 °F. The formula applies only at or below 50 °F with a wind above 3 mph.
At what wind chill does frostbite occur?
Environment and Climate Change Canada links wind chill to frostbite risk. At a wind chill of −28 to −39 on the Celsius scale, exposed skin can freeze in 10 to 30 minutes; at −40 to −47 in 5 to 10 minutes; at −48 to −54 in 2 to 5 minutes; and at −55 or colder in under 2 minutes. A wind chill of −28 °C is about −18 °F. The National Weather Service gives the example of 0 °F with a 15 mph wind, a wind chill of −19 °F, where exposed skin can freeze in 30 minutes. Frostbite needs an air temperature below freezing.
Does wind chill affect cars and pipes?
No. Wind chill describes heat loss from exposed skin, so it applies only to people and animals. Wind makes a car radiator, a water pipe or any other object cool faster, but the object cannot drop below the actual air temperature. In the National Weather Service example, with an air temperature of −5 °F and a wind chill of −31 °F, the radiator will not get colder than −5 °F. Water in a pipe can only freeze if the air around it is below 32 °F, whatever the wind chill says.
What is the difference between wind chill and the heat index?
Both describe how the weather feels on your body, but they cover opposite conditions. Wind chill combines air temperature and wind speed and applies only at or below 50 °F with a wind above 3 mph. The heat index combines air temperature and relative humidity for hot weather; the National Weather Service example is 96 °F at 65 percent humidity, which feels like 121 °F. Humidity was left out of wind chill because tests showed it changed the result by less than one degree. Neither index changes the actual air temperature.
When are cold weather advisories and extreme cold warnings issued?
Each National Weather Service office sets its own criteria, so the trigger depends on where you live. As an example, the NWS describes the Rochester, New York area, where an Extreme Cold Warning is issued when the apparent temperature, with or without wind, is expected to reach −25 °F or colder, and a Cold Weather Advisory covers air temperatures or wind chills from −15 °F to −24 °F. Environment and Climate Change Canada does not issue wind chill warnings; it issues cold warnings that include wind chill, with thresholds that vary by region. Follow the alerts for your area.
Sources & References
- National Weather Service. Understanding Wind Chill (formula, 50 °F and 3 mph limits, face height wind, objects, frostbite above freezing, humidity, children, local alert criteria). weather.gov
- National Weather Service. Wind Chill Chart (PDF). weather.gov
- National Weather Service. Service Change Notice 01 58: New Wind Chill Temperature Index Effective November 1, 2001. weather.gov
- National Weather Service Grand Junction. Wind Chill (Siple and Passel history). weather.gov
- Office of the Federal Coordinator for Meteorology. Report on Wind Chill Temperature and Extreme Heat Indices: Evaluation and Improvement Projects, FCM R19 2003 (both formulas, face level factor of 1.5, frostbite model, review of the old index). weather.missouri.edu
- Tew, M. A., Battel, G. and Nelson, C. A. Implementation of a New Wind Chill Temperature Index by the National Weather Service, American Meteorological Society, 2002 (metric formula, human trials). ams.confex.com
- Environment and Climate Change Canada. Wind chill and the Wind Chill Index (risk bands, freezing times, chart, forecast rules). canada.ca
- Environment and Climate Change Canada. Canada's Wind Chill Index poster (PDF; rapid rise in risk below −27, safety tips). canada.ca
- Environment and Climate Change Canada. Extreme cold and cold warnings. canada.ca
- Centers for Disease Control and Prevention. Preventing Frostbite and Preventing Hypothermia, reviewed 2026. cdc.gov, cdc.gov
- National Weather Service Miami. Beaufort Wind Scale. weather.gov
- National Weather Service. Heat Forecast Tools (heat index). weather.gov
- American Veterinary Medical Association. Cold weather animal safety and Walking or running with your dog. avma.org, avma.org
Results are informational estimates and not a substitute for local weather service warnings or medical advice. Every number on this page was recomputed with the same formulas the calculator uses. Reference data checked: 2026.