Ever step outside on a 20°F day and swear it feels much colder? That’s wind chill at work. Wind doesn’t lower the air temperature, but it pulls heat from exposed skin faster—sometimes fast enough to make frostbite a real risk. Use our calculator below to see how cold it really feels.
What Is Wind Chill?
Wind chill describes how cold it feels on exposed skin when wind and cold work together. It isn’t another reading on the thermometer. Instead, it translates the rate at which your body is losing heat into a temperature that’s easy to understand.
Here’s what’s happening: Your body continually warms a thin layer of air next to your skin. On a calm day, that layer provides a little insulation. When the wind blows, it sweeps that warmed air away, and your body has to work harder to replace the lost heat.
The stronger the wind and the colder the air, the faster that heat loss occurs. So an air temperature of 0°F can affect your body very differently on a calm day than it does when a 20-mph wind is blowing.
Does Wind Chill Actually Make the Air Colder?
No. Wind does not lower the actual air temperature. If your thermometer says 10°F, the air is still 10°F, no matter how hard the wind blows.
What changes is how quickly exposed skin loses heat. This also means wind chill can’t make an object colder than the actual air temperature. It may help an object cool to the air temperature faster, but it won’t push it below that temperature.
Why Wind Chill Matters
Wind chill becomes especially important when temperatures drop below freezing because faster heat loss increases the risk of cold-related injuries.
- Exposed skin cools faster as wind speed increases.
- Frostbite can develop surprisingly quickly in severe cold and wind.
- Hypothermia is also a danger when your body loses heat faster than it can replace it.
One useful distinction: Frostbite requires the actual air temperature to be below freezing. Wind chill alone can’t freeze exposed skin when the air temperature is above 32°F. Hypothermia, however, can occur even at temperatures above freezing, especially when someone is wet or exposed to wind for a long time.
How to Read the Wind Chill Chart
The calculator above is the quickest way to get your wind chill, but the chart below helps you see the bigger picture: how increasing wind speed changes heat loss across a range of cold temperatures.
Find the actual air temperature across the top of the chart and the wind speed along the left side. Where the two meet is the wind chill temperature.
For example, if the air temperature is 0°F and the wind is blowing at 15 mph, the wind chill is -19°F. At those conditions, exposed skin may develop frostbite in about 30 minutes.
The shaded areas show how frostbite risk increases as conditions become more severe. The current Wind Chill Temperature Index was developed by the U.S. National Weather Service and Environment Canada to better reflect how the human body loses heat in cold, windy weather.
Windchill Temperature ChartWind
Speed
(mph) | Temperature (°F) |
|---|
| Calm | 35 | 30 | 25 | 20 | 15 | 10 | 5 | 0 | -5 | -10 | -15 | -20 | -25 | -30 | -35 |
|---|
| 5 | 31 | 25 | 19 | 13 | 7 | 1 | -5 | -11 | -16 | -22 | -28 | -34 | -40 | -46 | -52 |
|---|
| 10 | 27 | 21 | 15 | 9 | 3 | -4 | -10 | -16 | -22 | -28 | -35 | -41 | -47 | -53 | -59 |
|---|
| 15 | 25 | 19 | 13 | 6 | 0 | -7 | -13 | -19 | -26 | -32 | -39 | -45 | -51 | -58 | -64 |
|---|
| 20 | 24 | 17 | 11 | 4 | -2 | -9 | -15 | -22 | -29 | -35 | -42 | -48 | -55 | -61 | -68 |
|---|
| 25 | 23 | 16 | 9 | 3 | -4 | -11 | -17 | -24 | -31 | -37 | -44 | -51 | -58 | -64 | -71 |
|---|
| 30 | 22 | 15 | 8 | 1 | -5 | -12 | -19 | -26 | -33 | -39 | -46 | -53 | -60 | -67 | -73 |
|---|
| 35 | 21 | 14 | 7 | 0 | -7 | -14 | -21 | -27 | -34 | -41 | -48 | -55 | -62 | -69 | -76 |
|---|
| 40 | 20 | 13 | 6 | -1 | -8 | -15 | -22 | -29 | -36 | -43 | -50 | -57 | -64 | -71 | -78 |
|---|
| 45 | 19 | 12 | 5 | -2 | -9 | -16 | -23 | -30 | -37 | -44 | -51 | -58 | -65 | -72 | -79 |
|---|
| 50 | 19 | 12 | 4 | -3 | -10 | -17 | -24 | -31 | -38 | -45 | -52 | -60 | -67 | -74 | -81 |
|---|
| 55 | 18 | 11 | 4 | -3 | -11 | -18 | -25 | -32 | -39 | -46 | -54 | -61 | -68 | -75 | -82 |
|---|
| 60 | 17 | 10 | 3 | -4 | -11 | -19 | -26 | -33 | -40 | -48 | -55 | -62 | -69 | -76 | -84 |
|---|
| Frostbite occurs in: | 30 minutes | 10 minutes | 5 minutes |
For example, when the temperature is 15°F and the wind speed is 30 miles per hour, the windchill, or how cold it feels, is -5°F.
How Is Wind Chill Calculated?
If you’re curious about what’s happening behind the calculator, the National Weather Service uses this formula:
Wind Chill = 35.74 + 0.6215T – 35.75(V0.16) + 0.4275T(V0.16)
Where:
- T = air temperature in degrees Fahrenheit
- V = wind speed in miles per hour
The formula is used when the air temperature is 50°F or colder and the wind speed is greater than 3 mph. Outside those conditions, the National Weather Service does not define a wind chill temperature.
You certainly can work through the formula yourself—but that’s why we built the calculator above!
When Does Wind Chill Become Dangerous?
There isn’t one magic wind chill number at which cold weather suddenly becomes dangerous. Risk increases as the temperature falls, the wind strengthens, and the amount of time you spend outdoors increases.
The two cold-weather hazards to know are frostbite and hypothermia. They’re related to cold exposure, but they aren’t the same thing.
Frostbite
Frostbite happens when skin and underlying tissues begin to freeze. Fingers, toes, ears, nose, cheeks, and chin are especially vulnerable because they’re often exposed or farthest from the body’s core.
Watch for numbness and skin that turns white or grayish-yellow or feels unusually firm or waxy. If you suspect frostbite, get out of the cold and seek medical care. Don’t rub or massage frostbitten skin, and don’t use a heating pad, fire, or other direct heat on numb skin.
Hypothermia
Hypothermia occurs when the body loses heat faster than it can produce it and the body’s core temperature becomes dangerously low.
Warning signs in adults can include shivering, exhaustion, confusion, fumbling hands, memory loss, slurred speech, and drowsiness. Hypothermia is a medical emergency, so get the person to a warm place and seek medical help immediately.
And remember: Hypothermia isn’t limited to brutally cold days. It can occur in cool weather, too, especially when a person becomes chilled by rain, sweat, cold water, or prolonged wind.
How to Stay Safe in Dangerous Wind Chill
The colder the wind chill, the more important it is to reduce both exposed skin and the amount of time you spend outside.
- Check the forecast before heading out. Pay attention to Cold Weather Advisories and Extreme Cold Watches or Warnings from the National Weather Service.
- Cover exposed skin. Protect your face, ears, hands, and feet. Mittens generally keep fingers warmer than gloves.
- Dress in loose, warm layers. Layers trap insulating air, and an outer layer that blocks wind helps slow heat loss.
- Stay dry. Wet clothing pulls heat away from your body and can greatly increase your risk of hypothermia.
- Take breaks from the cold. In severe conditions, go inside periodically to warm up rather than waiting until you feel numb or exhausted.
- Know the warning signs. Numb skin, uncontrollable shivering, confusion, or unusual drowsiness are signals to get out of the cold.
For more ways to prepare for bitter weather, see our tips for staying warm in winter.
And the next time the forecast says 15°F but the wind makes it feel much colder, you’ll know exactly why. Check the calculator, pay attention to the wind chill, and dress for what your body will actually experience—not just the number on the thermometer.
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