What is wind chill?
Wind chill is how cold the air feels on exposed skin once wind is factored in. Your body warms a thin layer of air next to the skin, and wind keeps stripping that layer away, so you lose heat faster than you would in still air. The wind chill temperature, sometimes called the wind chill factor or feels like temperature, puts that faster heat loss on a familiar temperature scale.
Wind doesn't make anything colder than the air itself. A car engine or a pipe can't drop below the air temperature, however hard the wind blows. It only cools them faster.
How to calculate wind chill
This wind chill temperature calculator uses the National Weather Service wind chill formula, with T as the air temperature in °F and V as the wind speed in mph:
Wind chill (°F) = 35.74 + 0.6215T − 35.75(V^0.16) + 0.4275T(V^0.16)
At 25°F with a 20 mph wind, V^0.16 is about 1.615. The sum is 35.74 + 15.54 − 57.74 + 17.26, which gives a wind chill of about 11°F. Other units are converted to °F and mph first.
The formula applies at or below 50°F, so this calculator accepts −50°F to 50°F. Wind chill is only defined above 3 mph. At or below 3 mph the result is a rough figure, and it never reads warmer than the air itself.
Wind chill chart
Wind chill in °F, by air temperature across the top and wind speed down the side.
| Wind | 40°F | 30°F | 20°F | 10°F | 0°F | -10°F | -20°F | -30°F |
|---|---|---|---|---|---|---|---|---|
| 5 mph | 36 | 25 | 13 | 1 | -11 | -22 | -34 | -46 |
| 10 mph | 34 | 21 | 9 | -4 | -16 | -28 | -41 | -53 |
| 15 mph | 32 | 19 | 6 | -7 | -19 | -32 | -45 | -58 |
| 20 mph | 30 | 17 | 4 | -9 | -22 | -35 | -48 | -61 |
| 30 mph | 28 | 15 | 1 | -12 | -26 | -39 | -53 | -67 |
| 40 mph | 27 | 13 | -1 | -15 | -29 | -43 | -57 | -71 |
| 50 mph | 26 | 12 | -3 | -17 | -31 | -45 | -60 | -74 |
| 60 mph | 25 | 10 | -4 | -19 | -33 | -48 | -62 | -76 |
Frostbite risk levels
The risk level comes from Environment and Climate Change Canada's wind chill scale, which is published in °C. Stronger sustained winds can freeze skin faster than these times.
| Wind chill | Risk | Exposed skin can freeze in |
|---|---|---|
| 0 to −9°C | Low | — |
| −10 to −27°C | Moderate | — |
| −28 to −39°C | High | 10 to 30 minutes |
| −40 to −47°C | Very high | 5 to 10 minutes |
| −48 to −54°C | Severe | 2 to 5 minutes |
| −55°C or colder | Extreme | Under 2 minutes |
What the results mean
- Feels like: the wind chill, in the unit you chose for air temperature.
- Heat loss on exposed skin: an estimate of how fast bare skin at 33°C (91°F) loses heat, from the older Siple-Passel wind chill index: H = (10.45 + 10√V − V) × (33 − T), where V is wind speed in meters per second and T is air temperature in °C. H comes out in kilocalories per square meter per hour, and the calculator multiplies it by 1.1622 to show watts per square meter. The formula peaks at 25 m/s (about 56 mph), so above that speed it understates heat loss.
- Risk level and freezing time: what to expect at this wind chill. No freezing time appears above 32°F, because frostbite needs below-freezing air.
What this calculator leaves out
Wind chill is an estimate. It ignores sunshine, which can make it feel warmer. Wet skin or clothing, age, and health can all raise your real risk. Use it as a planning guide, not as medical or safety advice.
Frequently asked questions
What is wind chill?
It's the temperature that bare skin seems to feel when wind speeds up heat loss. At 25°F with a 20 mph wind, it feels like about 11°F.
How do you calculate wind chill?
Put the air temperature in °F and wind speed in mph into the National Weather Service formula above, or enter them in the calculator.
Is wind chill the same as the feels like temperature?
In cold weather, usually yes. Many forecasts label wind chill as "feels like," though some also blend in sun and humidity. In hot weather, the same label usually means the heat index.
Can pipes freeze because of wind chill?
Not if the air stays above 32°F. Wind only cools objects down to the air temperature, though it gets them there faster.
Why doesn't wind chill work above 50°F?
The formula was built for cold conditions. In mild weather, wind feels pleasant rather than dangerous, so no wind chill is defined.
What's changed
- Launched with the National Weather Service wind chill formula, frostbite risk levels, and exposed-skin heat loss.
References
- National Weather Service, Wind Chill Chart
the wind chill formula, its limits of 50°F and 3 mph, and why frostbite requires below-freezing air
- Environment and Climate Change Canada, Wind Chill and the Wind Chill Index
the risk levels and exposed-skin freezing times used in the frostbite table
- National Weather Service Central Region, Technical Attachment 93-4: Effect of Wind and Temperature on Humans - Revisited
the Siple-Passel heat loss formula, in kilocalories per square meter per hour, with wind in m/s and a skin temperature of 33°C