How long you can stay outside in extreme cold before getting frostbite

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Flickr/Hernán Piñera

Millions of Americans are contending with an extreme cold snap caused by the polar vortex this week.

Record-breaking temperatures in parts of Michigan, Illinois, Minnesota, Wisconsin, and the Dakotas are up to 50 degrees below the average for this time of year.

National Weather Service officials are issuing warnings about hypothermia and frostbite, urging people to take wind chill into account when deciding whether to go outdoors. “Feels like” forecasts give a more accurate sense of risk, since they’re based on the rate of heat loss from exposed skin.

This chart from the National Weather Service shows how long a person can be exposed to certain temperatures before frostbite is likely to set in.

windchill temperature chart

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National Weather Service

With a low of minus 55 degrees Fahrenheit with windchill, the weather in Minneapolis this week is life-threatening. Frostbite is likely within five minutes.

Frostbite occurs when skin and the underlying tissues below freeze, or, in extreme cases, die. Fingers, toes, ear lobes, cheeks, and the tip of the nose are the most susceptible, because the body prioritizes keeping your core and head warm at the cost of everything else. That means blood flow to extremities tends to be redirected when the body is exposed to extreme cold. Less blood flow means the skin freezes faster.

Usually, when body parts get too cold, they turn red and start to hurt. Symptoms of frostbite, however, can also include numbness, loss of feeling, and lack of skin color.

According to the Mayo Clinic, even though exposed skin is most vulnerable, frostbite still occurs on skin covered by gloves or other clothing.

Pay attention to signs of hypothermia

Extreme temperatures also bring higher risk of hypothermia – when your body loses heat faster than you can produce it.

When your body temperature drops below the typical 98.6 degrees Fahrenheit, your heart and other organs can’t work properly. If untreated, hypothermia can lead to heart failure, and eventually death.

Warning signs that your body temperature is dropping too far below normal include uncontrollable shivering, memory loss, disorientation, incoherence, slurred speech, drowsiness, and exhaustion, according to the Mayo Clinic.

Factors like body fat, age, alcohol consumption, and wetness can affect how long hypothermia takes to strike. Older people above age 65 are particularly susceptible, since the body’s response to cold can be diminished by medical conditions like diabetes, some medicines, and aging itself. As a result, hypothermia can develop in older adults after just a brief exposure to cold weather.

Falling into freezing water puts you in even more danger, since the body loses heat 25 to 30 times faster in cold water than in cold air.

A winter swimmer in icy water, Heilongjiang province, China.

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A winter swimmer in icy water, Heilongjiang province, China.
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Reuters/China Daily China Daily Information Corp – CDIC

For example, in water 32.5 degrees Fahrenheit or colder, you might not survive more than 15 to 45 minutes. You’ll undergo shock within the first two minutes, and experience some functional disability before 30 minutes, according to the US Coast Guard.

What to know about pets and frostbite

Dogs and other domestic animals can get frostbite and hypothermia, too.

When the temperature drops, areas farthest from a dog’s heart – like the tail, ears, nose, and paws – experience a drop in blood flow, similar to what happens in humans. This causes tissue damage.

The American Kennel Club notes that breed plays a factor in a dog’s susceptibility to frostbite. Siberian huskies and Alaska malamutes tend to be less prone to it, unsurprisingly, than short-haired breeds like pugs and French bulldogs. But experts caution against leaving any dog unattended outside for any period of time during extreme weather events like a polar vortex.

If dogs spend too much time exposed to extreme cold, their overall body temperatures can drop, which can be fatal. Hypothermic dogs can seem lethargic and stiff, and other signs of hypothermia include shivering, lack of coordination, and low heart rate.

A French bulldog sits outside wearing a coat.

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A French bulldog sits outside wearing a coat.
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Anne Duden/Getty

So as the polar vortex persists, it’s imperative that anyone affected minimize the time both you and your pet spend in the cold in order to decrease the chances of frostbite or hypothermia.