Wind Chill Calculator: Feels-Like Temperature in °F and °C

What is wind chill?

Wind chill is how cold it feels on exposed skin when the wind is blowing. Your body warms a thin layer of air next to your skin; wind strips that layer away, so you lose heat faster. The wind chill index turns that faster heat loss into a temperature: “it feels like −24 °C” means your face loses heat about as fast as it would at −24 °C in light wind.

It is a measure of heat loss from people, not of the air. The thermometer does not change, and objects — a car radiator, a pipe, a puddle — never cool below the air temperature, however strong the wind. The background above follows your figures: stronger wind streaks for more wind, cold mist and frost as the wind chill drops.

Wind chill formula

Since November 2001, the US National Weather Service and Environment Canada have used the same index. With the air temperature T and the wind speed V measured at 10 metres:

• °F and mph: wind chill = 35.74 + 0.6215T − 35.75V^0.16 + 0.4275TV^0.16
• °C and km/h: wind chill = 13.12 + 0.6215T − 11.37V^0.16 + 0.3965TV^0.16

The NWS uses it at 50 °F (10 °C) and below with winds above 3 mph (4.8 km/h). Environment Canada reports wind chill at 0 °C and below with winds of 5 km/h or more. Outside that range the calculator returns the air temperature and tells you why.

Worked example: −15 °C and 20 km/h. 20^0.16 = 1.615, so 13.12 + 0.6215 × (−15) − 11.37 × 1.615 + 0.3965 × (−15) × 1.615 = −24.2, which rounds to −24 °C — the same figure Environment Canada gives for those conditions.

Wind chill calculator in Celsius

Choose °C and enter the wind in km/h — the way Canadian and most other forecasts give it. If your forecast gives the wind in metres per second or knots, pick that unit; the calculator converts it to km/h (1 m/s = 3.6 km/h, 1 knot = 1.852 km/h) before using the metric formula. Every result is shown in both °C and °F.

The old wind chill index (before 2001) — historical only

The first wind chill index came from experiments by the Antarctic explorers Paul Siple and Charles Passel in the 1940s, who timed how fast water froze in a plastic cylinder in different winds. Its US version was in use until 2001. It was criticised for exaggerating the cold — a cylinder of water is not a face — and for using wind measured high above the ground.

The old values were much colder: at 0 °F and 20 mph, the old index gave about −39 °F and the current one gives −22 °F. The calculator shows the old figure only as a comparison — for example if you are reading an older book or chart. Use the current index for anything safety-related.

How to read the wind chill chart

The curve under your result shows how the wind chill falls as the wind rises, at your air temperature, with your wind marked. In the table, find the air temperature on the left and the wind speed across the top; the cell where they meet is the wind chill. It switches between °C/km/h and °F/mph with your temperature unit and outlines the cell closest to your figures. Shading follows Environment Canada’s risk bands:

Fahrenheit to Celsius (and back)

°C = (°F − 32) × 5 ÷ 9 and °F = °C × 9 ÷ 5 + 32. Handy anchors: 32 °F = 0 °C, 0 °F ≈ −17.8 °C, −40 °F = −40 °C (the one temperature that is the same in both). For wind, 1 mph = 1.609 km/h.

Wind chill and school

Many school districts and boards look at the morning wind chill when deciding on cold closures, late starts or bus cancellations — but every district has its own rule, and wind chill alone never guarantees a closure. To compare a morning with your district’s rule, use the cold day calculator. For snow and ice, use the snow day calculator, the ice day calculator or the Canadian version.

Frequently asked questions