How it's worked out
Wind chill = 35.74 + 0.6215 × T − 35.75 × V0.16 + 0.4275 × T × V0.16, with T the air temperature in °F and V the wind speed in mph. It's the formula the National Weather Service has used since 2001, and it applies at 50°F or colder with wind over 3 mph. Outside that range the calculator shows the air temperature.
Reading it
Wind chill is how cold it feels on exposed skin, and it's the number that drives frostbite. It doesn't change how cold a piece of steel gets: equipment, water lines and concrete only cool to the air temperature. The NWS wind chill chart shows how fast frostbite can set in at each value.
On the job
- Plan warm-up breaks and a warm place to take them, and shorten exposure as the wind chill drops.
- Cover exposed skin, and keep spare dry gloves and liners on hand. Wet clothing loses most of its insulation.
- Watch for numbness, white or grayish skin, shivering that won't stop and slurred speech, and get the worker warm right away.