On a cold winter day, the actual air temperature does not always tell the whole story. When wind blows over exposed skin, it removes the thin layer of warm air your body naturally generates, making the temperature feel significantly colder than the thermometer reads. This effect is called wind chill. The National Weather Service (NWS) developed the current Wind Chill Temperature index in 2001 based on human trials at the Defense and Civil Institute of Environmental Medicine in Toronto, where 12 volunteers walked on a treadmill in a wind tunnel with thermal sensors on their faces. The CDC and NIOSH updated their cold stress guidelines in March 2026, reinforcing wind chill as a critical factor in preventing frostbite and hypothermia among outdoor workers. Understanding wind chill helps you dress appropriately, plan outdoor activities safely, and assess frostbite risk in cold conditions.
What This Calculator Does
Enter the current air temperature and wind speed to calculate the apparent temperature as felt on exposed human skin. The calculator also provides a frostbite risk assessment based on NWS guidelines.
For related weather tools, try our Heat Index Calculator for apparent temperature in hot and humid conditions, or our Dew Point Calculator to understand moisture levels in the air. You can also use our Temperature Calculator for converting between Fahrenheit and Celsius.
Inputs Required
- Air Temperature: The actual temperature in Fahrenheit or Celsius
- Wind Speed: Wind speed in mph or km/h
Outputs Provided
- Wind Chill Temperature: How cold the air feels on exposed skin
- Feels Colder By: The difference between actual and apparent temperature
- Frostbite Risk Level: Safe, Low Risk, Caution, High Risk, or Extreme
How the Calculation Works
The wind chill formula used in this calculator is the one adopted by the NWS and Environment Canada in 2001. It is based on human facial tissue cooling rates at walking speed (approximately 3 mph or 4.8 km/h). The NWS calculates wind speed at an average height of 5 feet, the typical height of an adult human face, based on readings from the national standard anemometer height of 33 feet. The formula assumes no impact from the sun (clear night sky conditions). Bright sunshine may increase the wind chill temperature by 10 to 18 degrees Fahrenheit.
Wind Chill (F) = 35.74 + 0.6215T - 35.75(V^0.16) + 0.4275T(V^0.16)
where T = temperature (F), V = wind speed (mph)
Wind Chill (C) = 13.12 + 0.6215T - 11.37(V^0.16) + 0.3965T(V^0.16)
where T = temperature (C), V = wind speed (km/h)
This formula is only valid when temperature is at or below 50 degrees Fahrenheit (10 degrees Celsius) and wind speed is at or above 3 mph (4.8 km/h). At higher temperatures, wind has a cooling effect through evaporation rather than sensible heat loss, which is calculated differently using the Heat Index. The NWS found during testing that relative humidity was an insignificant parameter, affecting the outcome by less than 1 degree, so it was excluded from the formula for simplicity.
How to Use the Calculator
- Select your preferred unit system (Fahrenheit/mph or Celsius/km/h)
- Enter the current outdoor air temperature
- Enter the current wind speed
- View the wind chill temperature and frostbite risk level
Example Calculation
- Air Temperature: 20 degrees F
- Wind Speed: 25 mph
- Wind Chill: approximately 3 degrees F
- Feels Colder By: 17 degrees F
- Risk: Caution, frostbite possible in 10 to 30 minutes
Real-World Scenarios
Planning a Winter Run in Minneapolis
A 34-year-old runner in Minneapolis checks the weather before her morning run. The temperature reads 28 degrees F, and she assumes light gloves are sufficient. The calculator shows that a 15 mph wind produces a wind chill of 15 degrees F, prompting her to add a face covering, thermal base layer, and warmer gloves to prevent frostbite on exposed cheeks. The NWS notes that wind chill testing was conducted on adult subjects only, and recommends being even more cautious with children, seniors, and persons with compromised health.
School Outdoor Recess in Fargo
A school administrator in Fargo uses the calculator to confirm wind chill is above the safety threshold before allowing students outside for recess. A 25 degree F temperature with 20 mph wind produces a wind chill of 11 degrees F, below the district's minimum threshold of 15 degrees F for outdoor activities. The administrator keeps recess indoors. The CDC and NIOSH cold stress guidelines, updated in March 2026, emphasize that children are particularly vulnerable to cold-related illness because they have a larger surface-area-to-mass ratio than adults.
Construction Crew in Billings
An outdoor construction crew in Billings uses the calculator to assess working conditions before starting their shift. At -5 degrees F with 15 mph winds, the wind chill drops to -26 degrees F. OSHA's cold stress guide recommends mandatory warm-up breaks every 20 to 30 minutes under these conditions. The site supervisor implements a work schedule with 30-minute outdoor rotations followed by 15-minute warm-up breaks in a heated trailer. The NWS now issues Extreme Cold Warnings when the apparent temperature is expected to fall at or below -25 degrees F, and Cold Weather Advisories when it falls between -15 and -24 degrees F.
Common Mistakes to Avoid
- Ignoring wind speed in weather checks: A temperature of 25 degrees F seems manageable, but with 30 mph winds the wind chill can drop well below 0 degrees F. Always check both temperature and wind speed before heading outdoors in winter
- Assuming wind chill affects inanimate objects: The NWS explicitly states that wind chill only describes human skin cooling. It does not freeze a car engine faster or change pipe freezing temperatures. Inanimate objects cool to the actual air temperature, not the wind chill temperature
- Underestimating overnight exposure: Sleeping outdoors or in unheated spaces with wind exposure carries a much higher frostbite risk than brief outdoor activity. The NWS wind chill formula assumes walking speed (3 mph), so standing still or sleeping reduces the body's own heat generation and increases risk beyond what the calculator shows
- Confusing frostbite and hypothermia: Frostbite is tissue freezing, which requires the actual air temperature to be below freezing. Hypothermia is a dangerous drop in core body temperature that can occur even above 40 degrees F if you are wet and chilled. The CDC notes that wind chill increases hypothermia risk even when the actual temperature is above freezing
Limitations of This Calculator
The NWS wind chill formula is valid only for temperatures at or below 50 degrees F (10 degrees C) and wind speeds at or above 3 mph (4.8 km/h). The formula assumes clear night sky conditions with no solar radiation. Bright sunshine can increase the apparent temperature by 10 to 18 degrees F, which this calculator does not account for. The formula is based on adult human facial tissue and may not accurately represent risk for children, who have different surface-area-to-mass ratios. The NWS did not test child volunteers for safety reasons. The frostbite timelines are approximate and assume exposed, unprotected skin. Wind chill does not apply to inanimate objects. The formula does not account for wet clothing, which dramatically increases heat loss, or for physical exertion level, which generates additional body heat. For comprehensive cold weather safety planning, consult the CDC and NIOSH cold stress guidelines.
Authoritative Research and Resources
- NWS Wind Chill Chart and Formula - The official National Weather Service wind chill temperature index, including the formula, frostbite timeline chart, and frequently asked questions. The index calculates wind speed at 5 feet (adult face height) and is based on heat transfer theory from human trials conducted in 2001.
- CDC and NIOSH Cold Stress Guidelines (Updated March 2026) - The National Institute for Occupational Safety and Health guidelines on cold-related illnesses including hypothermia, frostbite, trench foot, and chilblains. Updated in March 2026 with current recommendations for outdoor workers.
- OSHA Winter Weather and Cold Stress Guide - The Occupational Safety and Health Administration's resource for employers and workers on preventing cold-related illness, including recommended warm-up break schedules and personal protective equipment for cold environments.