Stay safe—and know the signs to watch for—if you're spending time outdoors in subzero temperatures.

By Amanda MacMillan
Updated: January 31, 2019

The news this week is all about the weather: Meteorologists are warning of deep freezes in the northeast and record low temperatures in the midwest in the coming days—with states like Illinois and Minnesota predicted to have wind chills as low as -50 and -60 degrees Fahrenheit.

In Chicago, forecasters expect Wednesday’s high temperature to be 14 degrees—the lowest high temperature for a single day since record-keeping began, according to the New York Times, and warmer than Antarctica, CNN notes. Health officials are warning people to stay indoors, check on their neighbors, and avoid wearing wet clothing, which loses its ability to insulate.

One big concern about this type of extreme cold is frostbite, says Stephanie Lareau, MD, assistant professor of emergency medicine at Virginia Tech Carilion School of Medicine. But despite its relative frequency, there’s a lot people don’t know about this condition, Dr. Lareau says. Here’s what she wants everyone to know, and how you can protect yourself in the cold.

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How do you know if you have frostbite?

Frostbite occurs when blood flow to the body’s extremities slows down, and parts of a person’s body—often the fingers, toes, or nose—can freeze as a result. It doesn’t occur all at once, says Dr. Lareau, and it can sneak up on people who are spending prolonged amounts of time outdoors.

“The first warning signs that you are at risk for frostbite is when body parts become cold,” says Dr. Lareau. “This is typically followed by burning and stinging, and then the body parts start to lose sensation and feel like pins and needles. This is followed by numbness.”

Ultimately, people with frostbite start to lose their fine motor skills and become increasingly uncoordinated, says Dr. Lareau. Thankfully, she adds, most people will recognize the beginning stages of frostbite and have time to seek warmth and stop the process.

Why do people get frostbite?

The simplest answer for as to why people get frostbite is because they’re spending too long outdoors in freezing temperatures. However, says Dr. Lareau, some people are at greater risk than others.

Certain medications, alcohol use, and lack of appropriate clothing or shelter can predispose people to frostbite, she says. Very young or very old people, and people with poor circulation due to other health conditions, are also at greater risk of developing frostbite.

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What does frostbite look like?

Frostbite severity isn’t always obvious when looking at an affected body part, says Dr. Lareau. Initially, the extremity will first look red—a stage that doctors call “frostnip,” she says.

As frostbite progresses, the skin starts to look pale. “That’s when you need to become worried, get out of the cold, and seek medical treatment,” she says. In late stages, a frostbitten body part can become covered in blood blisters or even turn black.

John van Hasselt - Corbis/Getty Images

How fast can frostbite occur?

The time it takes to develop frostbite depends on the temperature and windspeed, and the National Weather Service offers a handy Wind Chill Chart to help people determine what (and how long) is dangerous.

When the temperature is 0 degrees with 15 mile-per-hour winds, for example, frostbite can occur in about 30 minutes of exposure. But on very windy days with subzero temperatures, says Dr. Lareau, it can happen in as little as five minutes.

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Can you die from frostbite?

People don’t usually die from frostbite itself, but it can cause permanent damage to extremities like fingers and toes—which may need to be amputated. However, frostbite typically occurs along with hypothermia, which can be deadly.

Seeking medical attention as quickly as possible, and stopping the freezing process, is very important for avoiding long-term consequences from frostbite, says Dr. Lareau. “The degree of the injury really determines what sort of recovery someone will have,” she says.

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How is frostbite treated?

If people suspect they’ve developed frostbite, the best thing they can do is get inside and get warm, says Dr. Lareau. However, if they’re on long expeditions or in a remote area, it’s important not to rewarm hands or feet until they can be kept warm, she warns.

“Each time freezing injury occurs, ice crystals form,” she says. “If something re-freezes, this creates more damage.” If hands are numb, she says, you also shouldn’t rub them together or warm them over an open flame, she adds, because friction causes tissue damage, and it’s easy to burn yourself when you can’t feel the heat.

At medical facilities, some clot-busting medications (like those used for stroke victims) can be used to stop or reverse some damage from severe frostbite. In remote areas, bandaging the extremity in a bulky dressing—and evacuating to a warmer, indoor area—is the best initial treatment, she says. Once indoors, it’s best to rewarm extremities in a warm-water bath. (Aim for the temperature of a hot tub, but no higher.)

But the best way to avoid damage from frostbite is to prevent it in the first place, of course: Wear appropriate clothing and keep skin covered when spending time outdoors in the cold. Pay attention to weather alerts—and to strange symptoms like tingling and numbness—to keep yourself safe.
