Wind chill is what the air feels like on your skin when wind is moving
Wind chill is a number that tells you how cold the air feels when wind is blowing. It is not the actual temperature — it is lower, because moving air strips heat away from your skin faster than still air does. The National Weather Service calculates wind chill by combining the actual air temperature with the wind speed, and the result is always lower than the temperature alone.
You cannot measure wind chill with a thermometer. A thermometer measures only temperature. Wind chill is a calculation that accounts for how fast the wind is moving, and it matters because it tells you how quickly exposed skin can freeze or how fast you can lose body heat outdoors.
Key Takeaways
- Wind chill combines air temperature and wind speed into a single number that represents how cold the air feels on exposed skin.
- The National Weather Service wind chill formula requires the actual air temperature in Fahrenheit and wind speed in miles per hour.
- You can calculate wind chill by hand using the official formula, or look it up in a wind chill chart or online calculator.
- Wind chill only applies when the temperature is 50°F or below and the wind speed is above 3 miles per hour.
- The same wind chill value can result from different combinations of temperature and wind speed — for example, 20°F with 20 mph wind feels the same as 0°F with 10 mph wind.
The National Weather Service wind chill formula
The National Weather Service uses this formula to calculate wind chill:
Wind Chill (°F) = 35.74 + 0.6215T − 35.75(V^0.16) + 0.4275T(V^0.16)
In this formula, T is the air temperature in Fahrenheit, and V is the wind speed in miles per hour. The small raised numbers (0.6215, 0.16, and 0.4275) are constants that the National Weather Service determined through research on how fast skin loses heat in different wind conditions.
To use this formula by hand, you need a calculator that can handle exponents. The part that trips most people up is V^0.16, which means you raise the wind speed to the power of 0.16. For example, if the wind speed is 20 miles per hour, you calculate 20^0.16, which equals about 1.516. Once you have that number, you plug it into the rest of the formula with your temperature.
Step-by-step calculation with a real example
Let's say the air temperature is 20°F and the wind speed is 15 miles per hour. Here is how to work through the formula:
- Start with the temperature: T = 20
- Calculate V^0.16: 15^0.16 = 1.4816 (rounded)
- Multiply 35.75 by that result: 35.75 × 1.4816 = 52.97
- Multiply 0.4275 by the temperature by V^0.16: 0.4275 × 20 × 1.4816 = 12.68
- Now plug everything into the full formula: 35.74 + (0.6215 × 20) − 52.97 + 12.68
- Simplify: 35.74 + 12.43 − 52.97 + 12.68 = 7.88
- The wind chill is approximately 8°F
This means that at 20°F with a 15 mph wind, the air feels like it is about 8°F on exposed skin. The difference between the actual temperature (20°F) and the wind chill (8°F) is 12 degrees — that is how much colder the wind makes it feel.
Using a wind chill chart instead of the formula
If you do not want to do the math, the National Weather Service publishes a wind chill chart that shows the result for every combination of temperature and wind speed. You find your temperature along the left side of the chart and your wind speed across the top, then read where they meet. The chart covers temperatures from 50°F down to −60°F and wind speeds from 5 mph up to 60 mph.
Wind chill charts are printed on many weather station displays, posted in schools and workplaces, and available free on the National Weather Service website. They are faster than calculating by hand and just as accurate for practical purposes. Many people print one and keep it in their car or home during winter.
When wind chill does and does not explore
Wind chill only matters when two conditions are both true: the air temperature must be 50°F or colder, and the wind speed must be above 3 miles per hour. If the temperature is above 50°F, wind does not make the air feel significantly colder to your skin, so the National Weather Service does not calculate wind chill. If the wind is calm or moving slower than 3 mph, the effect is too small to measure.
On a still day with no wind, there is no wind chill — only the actual temperature matters. On a very windy day with warm air, wind chill is not calculated because the temperature is above the threshold. Wind chill is most relevant during winter storms or cold snaps when both temperature and wind speed are high.
Why the same wind chill can come from different conditions
Because wind chill depends on both temperature and wind speed, many different combinations produce the same result. For example, 0°F with a 20 mph wind produces a wind chill of about −19°F. But 20°F with a 40 mph wind also produces a wind chill of about −19°F. The faster wind at a warmer temperature feels the same on your skin as slower wind at a colder temperature.
This is why weather forecasters sometimes report wind chill instead of temperature alone — it gives you a better sense of the actual danger. A person standing outside at −19°F wind chill will lose body heat at the same rate whether the conditions are 0°F and calm or 20°F and very windy. The wind chill number tells you what matters for your safety: how fast you are losing heat.
Online calculators and weather service tools
The National Weather Service website has a free wind chill calculator where you enter the temperature and wind speed and it returns the result when ready. Many weather apps and websites also include wind chill in their forecasts, so you do not have to calculate it yourself. If you are checking conditions before going outside, your local National Weather Service office will have the current wind chill posted along with the temperature.
Some weather stations and outdoor thermometers have wind chill built in — they measure both temperature and wind speed and display the wind chill automatically. These are convenient if you check conditions often, though they cost more than a basic thermometer.
Frequently Asked Questions
Is wind chill the same as the "feels like" temperature?
Wind chill and "feels like" temperature are related but not identical. Wind chill accounts only for wind and temperature. "Feels like" temperature may also include humidity, sun exposure, and other factors. In winter, wind chill is usually the main driver of how cold it feels, but on a humid day with no wind, humidity can make the air feel colder than the temperature alone.
Can wind chill go below the actual temperature by any amount?
Wind chill can be much lower than the actual temperature, but the difference depends on wind speed. At 0°F with no wind, there is no wind chill effect. At 0°F with a 35 mph wind, the wind chill drops to about −35°F — a 35-degree difference. The stronger the wind, the larger the gap between temperature and wind chill.
Why does the wind chill formula use those specific numbers?
The National Weather Service developed the formula through research on how fast exposed skin loses heat in different wind and temperature conditions. The constants in the formula (0.6215, 0.16, and 0.4275) were calculated to match real measurements of heat loss. The formula was updated in 2001 to be more accurate than the older version.
Do I need to know wind chill if I am just checking the weather?
If you are dressing for the day or planning outdoor activities, wind chill is useful because it tells you how cold it will actually feel. Most weather forecasts include wind chill during winter, so you can see it without calculating it yourself. If the forecast shows a low wind chill, you know to dress warmer or limit time outside.