NWS Reference Chart
Wind Chill Chart & Frostbite Times
The official NWS wind chill chart shows how wind speed and air temperature combine to produce the apparent temperature your skin feels. Frostbite times tell you exactly how long you have before exposed skin freezes.
The NWS Wind Chill Formula
T= air temperature in °F | V= wind speed in mph | Applies when T ≤ 50°F and V > 3 mph
Wind Chill Temperature Chart (°F)
Rows = air temperature. Columns = wind speed. Cells below -20°F are highlighted — that's the school closure threshold for most northern districts.
| Temp °F ↓ / Wind mph → | 5 | 10 | 15 | 20 | 25 | 30 | 35 | 40 | 45 | 50 | 55 | 60 |
|---|---|---|---|---|---|---|---|---|---|---|---|---|
| 40° | 36° | 34° | 32° | 30° | 29° | 28° | 28° | 27° | 26° | 26° | 25° | 25° |
| 35° | 31° | 27° | 25° | 24° | 23° | 22° | 21° | 20° | 19° | 19° | 18° | 17° |
| 30° | 25° | 21° | 19° | 17° | 16° | 15° | 14° | 13° | 12° | 12° | 11° | 10° |
| 25° | 19° | 15° | 13° | 11° | 9° | 8° | 7° | 6° | 5° | 4° | 4° | 3° |
| 20° | 13° | 9° | 6° | 4° | 3° | 1° | 0° | -1° | -2° | -3° | -3° | -4° |
| 15° | 7° | 3° | 0° | -2° | -4° | -5° | -7° | -8° | -9° | -10° | -11° | -11° |
| 10° | 1° | -4° | -7° | -9° | -11° | -12° | -14° | -15° | -16° | -17° | -18° | -19° |
| 5° | -5° | -10° | -13° | -15° | -17° | -19° | -21° | -22° | -23° | -24° | -25° | -26° |
| 0° | -11° | -16° | -19° | -22° | -24° | -26° | -27° | -29° | -30° | -31° | -32° | -33° |
| -5° | -16° | -22° | -26° | -29° | -31° | -33° | -34° | -36° | -37° | -38° | -39° | -40° |
| -10° | -22° | -28° | -32° | -35° | -37° | -39° | -41° | -43° | -44° | -45° | -46° | -48° |
| -15° | -28° | -35° | -39° | -42° | -44° | -46° | -48° | -50° | -51° | -52° | -54° | -55° |
| -20° | -34° | -41° | -45° | -48° | -51° | -53° | -55° | -57° | -58° | -60° | -61° | -62° |
| -25° | -40° | -47° | -51° | -55° | -58° | -60° | -62° | -64° | -65° | -67° | -68° | -69° |
| -30° | -46° | -53° | -58° | -61° | -64° | -67° | -69° | -71° | -72° | -74° | -75° | -76° |
| -35° | -52° | -59° | -64° | -68° | -71° | -73° | -76° | -78° | -79° | -81° | -82° | -84° |
| -40° | -57° | -66° | -71° | -74° | -78° | -80° | -82° | -84° | -86° | -88° | -89° | -91° |
| -45° | -63° | -72° | -77° | -81° | -84° | -87° | -89° | -91° | -93° | -95° | -97° | -98° |
Frostbite Risk Times by Wind Chill
How long exposed skin can safely be outside before frostbite begins. These are approximate times based on NWS guidance for average adult skin.
| Wind Chill Range | Frostbite Time | Risk Level |
|---|---|---|
| 0°F to -9°F | > 60 minutes | Low |
| -10°F to -19°F | 30 minutes | Moderate |
| -20°F to -29°F | 15 minutes | High |
| -30°F to -39°F | 10 minutes | Very High |
| -40°F to -49°F | 5 minutes | Severe |
| Below -50°F | < 5 minutes | Extreme |
Quick Frostbite Lookup
Select a temperature and wind speed to see the wind chill and frostbite risk instantly.
Select values above to see your result
School Cold-Day Thresholds by Region
When wind chill hits these thresholds, districts cancel school for cold alone — even with zero snow on the ground.
| Region | Cold Day Wind Chill Threshold | Cold Days Per Winter |
|---|---|---|
| Minnesota / Dakotas | Below -35°F | 2–4 |
| Wisconsin / Michigan | Below -25°F | 1–3 |
| Illinois / Ohio | Below -20°F | 1–2 |
| Pennsylvania / New York | Below -15°F | 0–1 |
| Virginia / Maryland | Below -10°F | Rare |
| Georgia / Carolinas | Below 0°F | Almost never |
The Trench Truth: The coldest school closures are the least publicized because "it was really cold" doesn't make dramatic news. But in Minnesota, Wisconsin, and the Dakotas, cold days — cancellations due to temperature alone with no snow — happen 2–4 times per winter. If wind chill is forecast below -20°F, check your snow day probability even with zero snow.
Cold Weather Safety Quick Reference
Layer Up
Wear 3+ layers: moisture-wicking base, insulating mid-layer, windproof shell. Cotton kills — it traps sweat and freezes.
Cover Extremities
Frostbite hits fingers, toes, ears, and nose first. Insulated gloves, wool socks, and a hat that covers ears are non-negotiable below 0°F.
Watch for Signs
Numbness, white/grayish skin, and a 'wooden' feeling are early frostbite. Get inside immediately — don't rub the area.
Limit Exposure
At -20°F wind chill, exposed skin freezes in 30 minutes. At -40°F, it's under 10 minutes. Set a timer on your phone.
Stay Dry
Wet clothing loses insulation value almost entirely. If you sweat through a base layer, you're carrying a freezing blanket against your skin.
Check Before You Go
Use the SnowSense calculator to check conditions before heading out. If wind chill is below -15°F, reconsider any non-essential outdoor time.