In at least two small but notorious experiments, Castellani said, researchers observed what happened to people who sat in a chamber that was cooled to various temperatures. At -17 degrees Fahrenheit, results showed, it took about 30 minutes of exposure to cause frostbite.
But frostbite struck after just 10 minutes at -30 degrees Fahrenheit, and in just five minutes at -50 degrees Fahrenheit. The American College of Sports Medicine recommends “heightened surveillance” of athletes exercising outdoors when wind chills get down to -18 degrees Fahrenheit or below.
Wind chill measurements are more important than air temperatures when it comes to evaluating the dangers of cold weather, Castellani said, because the wind chill describes the temperature your skin is actually experiencing.
Fingers, toes, noses, earlobes and cheeks are most vulnerable to frostbite, he added, because peripheral areas are the first to experience vasoconstriction and blood loss after exposure to cold.
After being chilled for a while, many people experience something called cold-induced vasodilation (CIVD), which dilates the blood vessels in the extremities, causing a sudden hot, burning sensation.
People with good CIVD responses deal better with cold than those who easily lose circulation to their fingers and toes. People with a condition called Reynaud’s phenomenon, which disproportionately affects women, do not experience CIVD at all and are particularly vulnerable to frostbite.
Another concern on super-cold days is that frostbite can happen almost instantly if, say, you touch a frozen metal door handle or come into contact with gasoline, which can get down to -40 degrees Fahrenheit or colder and remain a liquid. Rolling down your car window to adjust the side window while driving fast on a cold day is also a bad idea.
“I was in Alaska a few years ago and even getting in and out of the car, you had better have gloves on,” Castellani said. “When the outside metal is -20 degrees Fahrenheit, you can get instantaneous frostbite touching supercooled materials.”
To protect yourself from the elements during cold fronts, Minson added, it’s important to avoid getting wet. The body loses heat 25 times faster when it’s wet than it does when it’s dry.
Most important of all is to dress well and cover exposed skin if you’re going to spend any time outside in the bitter cold.
“People have been able to survive in -80 to -100 degrees on Arctic expeditions as long as they were adequately protected and stayed out of the wind,” Minson said. “If you’re not protected, you’re in real trouble.”