How to stay safe in the cold, whether you’re facing a polar vortex, a 'bomb cyclone', or just hoping to squeeze in an outdoor run.

By Sarah Klein
January 08, 2018

We usually believe that nothing—not even the weather—can stop us from getting in a good workout. That’s what reflective leggings, waterproof jackets, and extra layers are for, right?

But when the temps dip way, way down, it may actually be healthiest to bundle up and stay put on the couch—or at least stick to a living room workout. That’s because brutally cold weather comes with some frightening health effects. Here’s what can happen to your body when it’s freezing (or below!) outside, and how you can protect yourself.

Frostbite

Your body recognizes sub-zero temps as a threat pretty quickly, and snaps into action to keep you alive. One of the first things that happens is blood flow slows to your fingers and toes. "The body tries to compensate for cold and prevent heat loss by shunting blood away from the skin and the extremities to maintain heat near vital organs," explains Ivan Miller, MD, medical director of emergency departments at Westchester Medical Center Health Network. "Those areas are allowed to get colder to protect the rest of the body."

This process keeps crucial internal organs safe, but it’s not always good news for fingers and toes. "If the temperature outside is below freezing, a toe or a fingertip might actually freeze," Dr. Miller explains, an injury known as frostbite. Frostbite is a bit like a burn, he explains, damaging different layers of tissue as the condition progresses. "A first-degree burn is similar to first-degree frostbite, which involves the most superficial layer of the skin," he says. As deeper layers of tissue freeze, the damage is harder to treat.

The first symptom of frostbite is probably one most people are familiar with: a little bit of numbness or tingling in the toes or fingers. (Frostbite also often affects the tip of the nose.) If you don’t warm up, the affected area can lose all feeling, then turn white or pale. And it can happen fast: It takes just minutes for to strike, according to the National Weather Service (NWS). (Check out this chart to calculate based on how cold and windy it is where you are.)

Exposed skin is most at risk, but you can still get frostbite on body parts bundled up in hats, gloves, and scarves. If any part of your body becomes numb when you’re out in the cold, go indoors pronto. Warm up the affected areas using your body with heat or warm water. ER docs do the same thing, Dr. Miller notes. "We do see frostbite in the emergency department, and sometimes [affected body parts] can be rewarmed and essentially thawed, and many people do regain function," he says.

Just avoid using hot water or heat from a heater or fireplace, which might burn the affected skin too easily, according to the NWS. Try not to rub frostbitten body parts together either, Dr. Miller warns. "You’ll lose some sensation due to the cold, and you could actually do damage to your skin with vigorous rubbing." If any area hurts for more than a few hours or starts to turn blue or black—signs of fourth-degree frostbite—see a doctor immediately.

RELATED: 5 Cold Weather Health Myths to Stop Believing

Shivering

It doesn’t have to be freezing outside for you to shiver, but it does happen quickly and easily when temperatures drop. Shivering might seem annoying if, say, you’re trying to hold your coffee mug steady, but it’s actually an impressive built-in safety mechanism for protection from the cold. The reason: Shivering helps the body stay warm, Dr. Miller explains. "Shivering is many, many little muscle contractions that generate heat."

While the results might not be quite as dramatic as moving around or jumping up and down, shivering is surprisingly effective at maintaining body temperature, at least in the short-term, Dr. Miller says. And even though shivering itself isn’t a major health threat, it is a sign you should go warm up. "It’s important to be mindful when you’re in the cold and feel yourself shivering," Dr. Miller says. "You really should seek a warmer environment." If you get colder, your health could be at risk (more on that later).

Muscles that aren’t busy contracting and shivering might simply tighten in cold weather. Just like you’re used to warming up cold muscles before a workout, cold weather can literally make you feel stiffer and tighter, Dr. Miller adds.

RELATED: How to Motivate Yourself to Go to the Gym on Cold, Dark Days

Hypothermia

The major health threat of not warming up when you can’t stop shivering is a dangerous dip in body temperature known as hypothermia. The NWS defines hypothermia as a decrease in body temperature below 95 degrees Fahrenheit. (Reminder: Around 98.6 is considered normal.) "The lower core body temperature goes, the more severe the symptoms," Dr. Miller says. Shivering becomes uncontrollable, and you might become confused or disoriented. "As hypothermia progresses, there can be a very dangerous lack of judgment that can lead people to make bad decisions and not get out of the cold," he says.

How long it takes to get hypothermia varies quite a bit from person to person, Dr. Miller says, and depends on factors like body size and composition, age, and how many layers you're wearing. Call 911 if you suspect someone has hypothermia. Without treatment, hypothermia can be fatal. While waiting for medical professionals, get the person indoors and warmed up with dry, warm clothing or blankets. Warm drinks can help, too.

Headaches

Cold weather isn’t just a figurative headache making your commute more cumbersome and your gym plans more treacherous. It could also be a literal pain: Fluctuations in barometric pressure are thought to trigger headaches or migraine in some sufferers, and certain winter storms bring sudden, drastic drops in pressure.

Cold temperatures themselves can also hurt, much like the pain from downing an ice cream too quickly. Brain freeze is a type of that occurs in response to sudden cold over the palate; inhaling cold air or simply encountering it externally can have similar effects, according to the International Classifications of Headache Disorders.

Runny nose and watery eyes

Very cold air also often happens to be very dry air. Because dry air doesn’t feel so good going into the lungs, the nose works to add moisture to the air you inhale. If the air you breathe is extra-dry, your nose has to add extra moisture, and when there’s a lot of fluid, some of it drips unpleasantly out of your nostrils. Researchers have affectionately dubbed this phenomenon .

Cold, dry air can also irritate the eyes, which, obviously, like to stay moist at all times. When your eyes are dry due to that wintery wind, you reflexively pump out extra liquid to compensate. Some of that is bound to trickle out—and hopefully won’t freeze your cheeks!

RELATED: 9 Reasons Your Eyes Are So Watery–and What to Do About It

Shortness of breath

Cold, dry air can also , especially in people with asthma, bronchitis, or other lung conditions, according to the American Lung Association. You might find that inhaling frigid air leads to wheezing, coughing, or some shortness of breath, particularly if you have one of those underlying conditions. However, you’ll probably know if this applies to you and the shortness of breath shouldn’t strike out of the blue. "That wheezing and coughing is something that happens every time they are exposed to the cold," Dr. Miller says.

If you do experience sudden shortness of breath, especially alongside chest pain, nausea, or other similar symptoms, seek emergency medical attention, as those could be signs of a heart attack. Heart attacks may be more common after shoveling snow, particularly among people who aren’t necessarily used to such vigorous exercise.

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Increased calorie burn

Your shiver-filled walk from the bus stop to your office isn't exactly going to replace a full-blown winter workout. But the silver lining to all this dreaded weather is that the mechanisms your body uses to try to keep you warm ramp up calorie burn, at least a little. "Efforts to maintain body temperature expend energy," Dr. Miller explains. Cold weather-induced shivering can activate brown fat and the hormone irisin, both of which can help the body burn burn fat.