EngineeringFormulaThermodynamics
Wind Chill Calculator
Calculate wind chill, the cold feels-like temperature, from air temperature and wind speed using the National Weather Service formula.
Wind chill estimates how cold moving air feels on exposed skin by combining air temperature and wind speed. This calculator uses the current National Weather Service wind-chill equation, returns the apparent temperature, and adds a cautious exposed-skin frostbite-time note when the result falls into a charted danger zone. Wind chill is a human heat-loss index, not a thermometer reading: it does not make objects or water colder than the real air temperature.
T · Actual air temperature, not an existing feels-like reading
V · Use sustained wind speed when possible
Solution
Enter cold-weather values. Defined for T ≤ 50°F and wind speed > 3 mph.
WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T V^0.16
Formula Sheet
- WCWind Chill
- TAir Temperature
- VWind Speed
Variables & Units
| Symbol | Variable | Description | Common Units |
|---|---|---|---|
| WC | Wind Chill | Apparent temperature felt on exposed skin in cold wind. | °F, °C |
| T | Air Temperature | Actual dry-bulb air temperature, converted to °F for the NWS formula. | °F, °C |
| V | Wind Speed | Wind speed converted to mph for the NWS formula; weather stations normally report wind measured near 10 m height. | mph, km/h, m/s |
How to Use This Calculator
- 01Enter the actual air temperature from a thermometer or forecast.
- 02Enter the wind speed, ideally the sustained wind from a weather observation rather than a brief gust.
- 03Use the calculator only for cold, windy conditions: air temperature at or below 50°F and wind speed above 3 mph.
- 04Select Calculate to see the wind chill, how many degrees colder it feels, and the approximate exposed-skin frostbite risk band.
- 05Compare the result with the frostbite-risk table below the examples before planning outdoor work, school travel, sports, or pet exposure.
How the Formula Works
The National Weather Service wind-chill formula is WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16, where T is air temperature in °F and V is wind speed in mph. The calculator converts metric inputs to those units before applying the formula.
Wind removes heat from exposed skin faster than calm air. The result is reported as an equivalent calm-air temperature: a wind chill of −20°F means exposed skin loses heat about like it would on a calm −20°F day.
The formula is defined only for temperatures at or below 50°F and wind speeds above 3 mph. Outside that range, this page shows a validation message instead of pretending the index applies.
Bright sun, clothing, wet skin, activity level, and individual health can change actual risk. The frostbite note is a planning warning for exposed skin, not a medical timer.
Because wind chill is a heat-loss index, it is most useful for people and animals with exposed skin. It is less useful for car engines, pipes, buildings, or stored objects, which approach the real air temperature rather than the wind-chill number.
Worked Example 01
5°F air with 30 mph wind
Known
- Air Temperature (T): 5°F
- Wind Speed (V): 30 mph
Formula
WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T V^0.16
Substitution
WC = 35.74 + 0.6215(5) − 35.75(30^0.16) + 0.4275(5)(30^0.16)
Result
WC ≈ −19°F
This matches the common NWS chart example: 5°F with a 30 mph wind feels near −19°F, a range where exposed skin can develop frostbite in about 30 minutes.
Worked Example 02
-10°F air with 20 mph wind
Known
- Air Temperature (T): -10°F
- Wind Speed (V): 20 mph
Formula
WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T V^0.16
Substitution
WC = 35.74 + 0.6215(-10) − 35.75(20^0.16) + 0.4275(-10)(20^0.16)
Result
WC ≈ −35°F
The air is already below zero, and the stronger heat loss from wind pushes the apparent temperature into the approximate 10-minute exposed-skin frostbite band.
Worked Example 03
Metric forecast: -15°C with 30 km/h wind
Known
- Air Temperature (T): -15°C = 5°F
- Wind Speed (V): 30 km/h ≈ 18.6 mph
Formula
WC = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T V^0.16
Substitution
WC = 35.74 + 0.6215(5) − 35.75(18.6^0.16) + 0.4275(5)(18.6^0.16)
Result
WC ≈ -16°F, or about -27°C
The calculator converts metric inputs into the NWS formula units internally, then reports the result back in the selected display unit. This is near the lower-risk edge of the 30-minute exposed-skin frostbite band.
Applications
- 01Checking outdoor work, school, travel, and event conditions during cold windy weather
- 02Estimating exposed-skin frostbite risk bands from forecast temperature and wind speed
- 03Comparing how much colder a stronger wind makes the same air temperature feel
- 04Deciding when gloves, face covering, shorter exposure, or schedule changes are prudent for outdoor tasks
Approximate exposed-skin frostbite risk bands
| Wind Chill | Approximate Exposed-Skin Risk |
|---|---|
| Above -18°F (-28°C) | Lower frostbite risk from wind chill alone |
| -18°F to -32°F (-28°C to -36°C) | Frostbite possible in about 30 minutes |
| -33°F to -47°F (-36°C to -44°C) | Frostbite possible in about 10 minutes |
| -48°F (-44°C) or colder | Frostbite possible in 5 minutes or less |
Assumptions
- 01Uses the 2001 National Weather Service / North American wind-chill temperature index.
- 02Air temperature must be at or below 50°F and wind speed must be above 3 mph.
- 03Assumes no warming from direct sunlight; bright sun can make conditions feel noticeably warmer.
- 04Wind speed is treated as sustained wind, not a short gust.
Where This Model Stops
- 01Not valid for warm-weather heat stress - use heat index or humidex methods for hot, humid conditions.
- 02Does not account for clothing, wet skin, sun exposure, exertion, age, or medical conditions.
- 03Does not mean objects cool below the actual air temperature; wind chill affects heat-loss rate, not the final temperature of inanimate objects.
- 04Does not replace official weather warnings, employer cold-stress procedures, school closure policies, or medical guidance for frostbite/hypothermia risk.
References
- [1]Understanding Wind Chill
National Weather Service
Official formula, applicability limits, no-sun assumption, and frostbite chart context.
- [2]Wind Chill
Environment and Climate Change Canada
Cross-reference for Celsius/km/h wind-chill equation and wind-speed measurement context.
- [3]Wind chill and the Wind Chill Index
Canada.ca
Reference for user-facing interpretation, exposed-skin frostbite risk, and object-temperature caveat.
Frequently Asked Questions
When is wind chill defined?
The National Weather Service defines wind chill only for air temperatures at or below 50°F and wind speeds above 3 mph. Above those limits, the index is not physically meaningful enough for this formula, so this calculator asks for colder or windier inputs instead of returning a fake precision result.
Can wind chill freeze water if the air temperature is above freezing?
No. Wind chill can make exposed skin lose heat faster, but objects and water cannot cool below the actual air temperature because of wind chill alone. If the air temperature is above 32°F, wind may cool water faster toward that air temperature, but it will not freeze it.
Should I use sustained wind speed or gust speed?
Use sustained wind speed for the normal wind-chill index. Gusts can briefly feel harsher and may increase risk, but using a short gust as the only input can overstate the typical condition.
Why does sunshine matter?
The NWS wind-chill formula assumes no direct sun. Bright sunshine can make the apparent temperature feel roughly 10°F to 18°F warmer than the wind-chill number, depending on conditions.
How is this different from the Dew Point Calculator?
Wind chill estimates cold-weather heat loss from exposed skin using temperature and wind speed. Dew point describes moisture in the air and condensation risk. They answer different questions, so a cold windy day uses wind chill while fog, condensation, and comfort-humidity checks use dew point.
Should I use wind chill for pets or livestock?
Wind chill can be a useful warning signal for animals too, especially when skin, ears, paws, or wet fur are exposed. Actual risk depends on breed, coat, shelter, age, health, and time outside, so use the number as a conservative planning cue rather than a precise safe-exposure timer.