What is wind chill? How the 'feels like' temperature can hasten frostbite.
As temperatures plummet and the winds howl this winter, you'll hear about the dangers of the "wind chill." So what is it?
The wind chill temperature is how cold people (and animals) feel while outside. Wind chill is based on the rate of heat loss from exposed skin caused by the combination of wind and cold, according to the National Weather Service.
As the wind increases, it draws heat from the body, driving down skin temperature and eventually the body's internal temperature.
“It’s how it feels when you’re out in cold weather with wind blowing,” Bob Oravec, a lead forecaster for the Weather Service at the Weather Prediction Center, told Popular Science.
What do wind chill numbers mean?
Wind chill makes it feel much colder than it really is, so it's been described as a "feels-like" number. If the temperature is 0 degrees and the wind is blowing at 15 mph, the wind chill is 19 degrees below zero.
Low wind chill numbers are a sign you need to dress for colder conditions. For example, when the wind chill is around 40 degrees below zero, exposed skin can freeze in as little as 10 minutes.
Wind chill chart shows when frostbite is a danger
A chart from the Weather Service shows the relationship between temperature, wind and how long before frostbite occurs.
The weather service began to include wind chill in their forecasts in the early 1970s, several decades after Antarctic explorers first published research about it in the late 1930s.
The U.S. and Canadian weather services revised the wind chill index in 2001, based on greater scientific knowledge and on experiments that tested how fast the faces of volunteers cooled in a wind tunnel with various combinations of wind and temperature.