Wind Chill Temperature Calculator

Wind chill: NWS 2001 formula explained

Wind chill (WC) is the temperature your skin actually feels. Wind speeds up convective heat loss by stripping away the warm layer of air sitting against your body, so the air feels colder than it really is. The standard NWS/MSC 2001 formula is WC = 13.12 + 0.6215·T − 11.37·V^0.16 + 0.3965·T·V^0.16, with T in °C and V in km/h. It only holds for T ≤ 10 °C and V ≥ 4.8 km/h. Take T = 0 °C and V = 30 km/h: the result is WC ≈ −10 °C. Once you drop below WC −27 °C frostbite risk climbs fast, and beyond that hypothermia becomes an immediate danger. This formula took over from the older Siple-Passel model (1945) after a joint US/Canadian study put volunteers in cold chambers. One thing it leaves out on purpose is humidity and solar radiation. On a damp, overcast day, those would drag the apparent temperature down even further.

Applications

It shows up in weather forecasting, where INMET issues wind-chill alerts for southern Brazil when cold fronts move through. It also feeds occupational safety for people working outdoors, under Brazil's NR-29 cold-exposure guidelines. Beyond that, you'll find it behind snow tourism and skiing, mountaineering, polar expeditions, advice on how many layers to wear, and the emergency warnings put out for the elderly and homeless populations during cold waves.

FAQ

Does wind chill affect objects too? No. It's about how human skin perceives the cold, nothing else. A parked car never gets colder than the actual air temperature. Wind just helps it reach that temperature sooner.

Why does the formula require V ≥ 4.8 km/h? Under that threshold the air is basically still, so the convective model no longer applies. At that point the perceived temperature is just the ambient air temperature.

Is wind chill the same as heat index? No. Wind chill is for cold weather with wind. The heat index is the opposite case, covering hot and humid conditions (T + relative humidity).