How cold does it really feel out there? Set the temperature and wind speed to get the official NWS wind chill — the feels-like temperature on exposed skin — plus how fast frostbite can set in and a full wind chill chart for planning ahead.
Frostbite is possible on prolonged exposure. Dress in layers and keep skin covered.
Wind chill chart (°F, wind in mph)
Wind ↓ / Temp →
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°
25 mph
29°
16°
3°
-11°
-24°
-37°
-51°
-64°
30 mph
28°
15°
1°
-12°
-26°
-39°
-53°
-67°
35 mph
28°
14°
0°
-14°
-27°
-41°
-55°
-69°
40 mph
27°
13°
-1°
-15°
-29°
-43°
-57°
-71°
Shading shows frostbite time on exposed skin: orange ≈ 30 min, light red ≈ 10 min, red ≈ 5 min.
📌 The NWS wind chill formula is defined only for temperatures at or below 50°F (10°C) and wind speeds of at least 3 mph (5 km/h) — the sliders stay inside that range. Above 50°F or in calmer air, wind chill is not reported because the cooling effect is negligible.
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The NWS wind chill formula
The calculator uses the formula adopted by the US National Weather Service and Environment Canada in November 2001:
where T is the air temperature in °F and V is the wind speed in mph. Unlike the 1945 original, which measured how fast water froze in a plastic cylinder, the 2001 revision models heat loss from a human face — the body part usually left exposed in winter. Scientists computed how wind accelerates heat transfer from skin at face level (about 5 feet), assumed a walking speed of 3 mph, and calibrated the model against clinical trials in which volunteers with temperature sensors on their faces walked on treadmills in a refrigerated wind tunnel.
Worked example
Say it is 5°F with a 30 mph wind. First, V0.16 = 300.16 ≈ 1.723. Then: WC = 35.74 + 0.6215 × 5 − 35.75 × 1.723 + 0.4275 × 5 × 1.723 = 35.74 + 3.11 − 61.61 + 3.68 ≈ −19°F. Air that reads 5°F on the thermometer feels like −19°F on your skin — cold enough for frostbite on exposed skin in about 30 minutes.
Frequently asked questions
Wind chill is how cold the air feels on exposed skin when wind is factored in. Your body warms a thin layer of air next to your skin; wind strips that layer away, so heat leaves your body faster and the air feels colder than the thermometer reading. Wind chill is a perceived temperature — the actual air temperature does not change.
No. Wind chill describes heat loss from warm-blooded skin, not from objects. Wind makes a car engine or a water pipe cool down to the air temperature faster, but it can never cool them below the actual air temperature. If it is 20°F with a wind chill of 0°F, your pipes will only ever reach 20°F.
The National Weather Service issues frostbite guidance based on wind chill: below about −18°F wind chill, exposed skin can freeze in 30 minutes or less. At −33°F wind chill frostbite can strike in around 10 minutes, and below −48°F in as little as 5 minutes. Fingers, toes, ears, nose, and cheeks freeze first — cover them completely in those conditions.
The old formula from 1945 was based on how fast water froze in a plastic cylinder in Antarctica, and it exaggerated the cooling effect. In 2001 the US and Canadian weather services replaced it with a model based on heat loss from a human face, calibrated with clinical trials on volunteers walking in a wind tunnel. The new values are typically 10–20 degrees "warmer" than the old chart for the same conditions.
The NWS formula was only validated for temperatures at or below 50°F and wind speeds of at least 3 mph. Above 50°F wind has little perceived cooling effect, and below 3 mph the air layer next to your skin is barely disturbed, so no wind chill value is defined or reported.