What is wind chill and what makes it dangerous?
Nashville and Middle Tennessee is facing "dangerous and potentially life-threatening" wind chills in the next couple of days.
Friday morning the wind chill will be close to -20 with an actual temperature close to 0, the National Weather Service in Nashville said.
Exposure to such extremes can cause frost bite in 15 to 20 minutes, the NWS said.
Latest updates: Nashville temperatures reach 0 degrees; wind chill warning in effect across Middle Tennessee
"Many have never experienced anything like this," the NWS said. "It's nothing to mess around with. Stay in, if you can. If you *have* to be outside, do it in short bursts and cover up skin!"
But what does the NWS mean when they talk about wind chill?
What is wind chill?
Wind chill is a used to describe what the air temperature feels like to the human skin, according to the NWS.
The colder the air temperature and the higher the wind speeds, the colder it will feel on the skin outside.
When the temperature remains the same, but wind speeds increase, it'll feel colder.
What to do:5 things to know to prepare for Nashville's upcoming deep freeze
Why does it feel colder?
As wind blows across your body, it takes the heat you naturally produce and blows it away, the NWS said. The faster the wind speed, the faster body heat is removed and the colder it'll feel.
Think of blowing on a hot bowl of soup. It's the same concept.
When does frostbite occur?
Frostbite times are calculated on a table that compares air temperatures to wind speeds.
Frostbite can occur when temperatures are as low as 10 degrees, if wind speeds are as high as 55-60 mph, according to the NWS. According to the table, frost bite under those conditions would occur in about 30 minutes.
On the opposite extreme, if temperatures reach 15 below zero, wind speeds are around 60 mph and wind chill is at -48, frost bite can set in in five minutes.
What is a wind chill warning?
Just like other types of weather alerts, wind chill notices come in levels.
Wind Chill Advisory: Be aware. Seasonable wind chill values are expected. Dress appropriately and cover exposed skin when outside.
The upside of cold weather: If you sell PVC pipes, milk, or tow cars, cold weather is big business
Wind Chill Watch: Be prepared. Dangerously cold wind chill values are possible. Adjust plans to avoid being outside during the coldest times of the day. Make sure your car has at least a half tank of gas and update your winter survival kit.
Wind Chill Warning: Take Action! Dangerous wind chill value are expected or occurring. Avoid going outside during the coldest times of the day. Dress in layers, cover exposed skin and make sure at least one person knows your whereabouts.
This article originally appeared on Nashville Tennessean: Nashville weather: What is wind chill and when is it dangerous
