This wind chill calculator computes how cold it actually feels on exposed skin from air temperature and wind speed, using the current National Weather Service formula — plus the frostbite timeline that turns the number into a decision.

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Why Wind Steals Heat

Your body warms a thin insulating layer of air at the skin; wind strips it away, and skin cools toward the air temperature at a wind-driven rate. The modern formula — 35.74 + 0.6215T − 35.75V^0.16 + 0.4275T·V^0.16 — was rebuilt in 2001 from human volunteer trials (the old Siple-Passel figures overstated the chill). Its summer mirror is our Heat Index Calculator. Part of our Other Calculators collection.

Worked Examples (Verified)

  • 20 °F with a 15 mph wind → wind chill 6 °F — the widget’s defaults: a walk that feels 14 degrees colder than the thermometer claims
  • 0 °F at 25 mph → −24 °F: the frostbite clock shrinks to ~15–30 minutes
  • −20 °F at 30 mph → ≈ −53 °F — ten-minute frostbite, the arithmetic behind polar and plains warnings
  • The diminishing lever: doubling wind from 10 to 20 mph at 20 °F drops the chill from 9 to 4 °F; from 30 to 60 mph buys only ~4 more — V^0.16 flattens fast, which is why any windbreak beats a thicker coat alone

Reading It Responsibly

  • Wind chill can’t push objects — or you, once insulated — below the actual air temperature; it accelerates the approach. Car radiators don’t care; exposed cheeks do.
  • Sunlight offsets it (clear midday sun can feel 10–15 °F warmer than the shade value), as does movement-generated heat until you stop.
  • Wet skin and wet clothing destroy insulation values far beyond the formula’s scope — cold rain near freezing kills more people outdoors than dry deep-freeze.
  • Frostbite times assume healthy adults with exposed skin; children, circulation conditions and alcohol all shorten them.

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Frequently Asked Questions

How is wind chill calculated?

With the NWS formula: 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16, for temperature T in °F and wind V in mph. At 20 °F and 15 mph it gives ≈ 6 °F of felt cold on exposed skin.

Why did wind chill values change in 2001?

The earlier formula derived from 1940s Antarctic water-bottle experiments and exaggerated cooling. Joint US–Canadian trials with human volunteers and modern heat-transfer modeling produced the current formula — lower (less alarming) numbers, better matched to how skin actually loses heat.

How fast does frostbite happen?

Per NWS guidance: ~30 minutes at wind chills near −10 to −25 °F, 10–15 minutes around −25 to −40 °F, and 5–10 minutes below −40 °F — for exposed skin. Noses, ears, cheeks and fingers go first; tingling that turns to numbness is the warning to heed immediately.

Does wind chill affect my car or pipes?

Only the speed of cooling, not the floor: nothing without internal heat falls below ambient air temperature from wind alone. Antifreeze and pipes are sized to the thermometer; skin is what the index serves.

What if the wind is calm?

Below ~3 mph the effect is negligible (and the formula isn’t calibrated there); on calm clear nights radiative cooling and cold-air pooling matter more than wind chill. This calculator flags out-of-range inputs rather than pretending precision.

Is this wind chill calculator free?

Yes — free, instant, no sign-up.