Why You *Always* Have to Pee When You’re Freezing Cold

...And more wacky ways your body reacts to winter weather.

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Freezing cold woman in winter
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Your blood vessels constrict

Your body is built to always maintain a stable core temperature of 37 degrees Celsius (that’s 98.6 degrees Fahrenheit). When the temperature in your environment drops, thermoreceptors in your skin sound the alarm, alerting an area of the brain called the hypothalamus, which acts like a thermostat dedicated to maintaining that 37 degree equilibrium, according to Robert Kenefick, PhD, research physiologist at the U.S. Army Research Institute of Environmental Medicine. One of the first actions the hypothalamus takes: It tightens the blood vessels in your arms, hands, feet, and legs. “Blood delivers heat to the skin,” says Gordon Giesbrecht, PhD, professor of thermophysiology at the University of Manitoba. “If you decrease blood flow to the skin, you decrease heat loss from the skin.”

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How to unclog a toilet without a plunger - hand flushing toilet
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You have to urinate

All that vasoconstriction forces fluid to concentrate in your core. This causes volume receptors that talk to your hypothalamus to say, “Hey, maybe you should get rid of some of that fluid—maybe you should pee.” It’s common, say, on the ski slopes for people to use the bathroom right before they head outdoors and then to feel like they need to go again shortly after being outside.

Here’s what it could mean if you’re always waking up at night to pee.

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Sick ill young woman feel cold covered with blanket sit on sofa watching movie on laptop, annoyed girl shiver freezing warming at home wrapped with plaid, no central heating problem and flu concept
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You shiver

Of course you shiver when it’s cold—duh! But the reason you do is utterly interesting. “When vasoconstriction isn’t doing enough to warm you, the hypothalamus tells your muscles to start contracting. One of the byproducts of muscle contraction is heat.” Garden-variety shivering produces about 100 watts of heat, says Giesbrecht. If you get cold enough to enter into mild hypothermia, you can produce 400 to 600 watts of heat through shivering.

Find out what it was like on the coldest day in Canadian history.

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Pool in winter
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You freeze much faster if wet

Why do little kids still shiver when they get out of a heated swimming pool in warm summer weather? “Water carries heat away from the body 25 times faster than air, so you can lose a great amount of heat very quickly when you’re wet,” says Kenefick. “Shivering is one way your body is trying to raise your core temperature back up.”

Here are more science facts you didn’t learn in school.

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Cocktail with ice on a table outside in the winter
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You make things worse if you drink alcohol

Think a flask filled with the strong stuff can keep you toasty? You might be dead wrong. The body’s first major reaction to cold is to constrict blood vessels, but  “alcohol does the opposite—it causes peripheral vasodilation,” explains Kenefick. “Those blood vessels widen and dump all this heat to the environment.” Your skin will feel warm, but that provides a false sense of security, because this really causes your core temperature to drop, which can lead in extreme cases to hypothermia.

Check out the gruesome effects of alcohol on the body.

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One woman with winter jacket and scarf doing outdoors recreation.
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You can become too cold if you dress too warmly

How’s this for irony? You’re outside in very cold weather shovelling snow, which is a lot of physical work. You’re contracting muscles and generating a lot of heat, so your core temperature actually goes up. “In this situation, your blood vessels dilate instead of constrict, and you start sweating. If that sweat then gets trapped in your clothing, then it can start sucking heat away from your body. That’s a recipe for hypothermia right there,” says Kenefick. The lesson: Don’t overdress if you know you’re going to be exercising vigorously.

Find out seven more mistakes to avoid when removing snow.

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how your body deals with freezing weather - Happy family of three, mother, father and son, in warm clothes, sitting close to each other and trying to warm up by fire outside in cold snowy winter weather, against snowbound forest background
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You scrunch down and huddle with others

When your body has constricted your blood vessels and made your muscles start shivering, you might also instinctually engage in social behaviours that help conserve heat. When you scrunch down and make yourself smaller, you lose less heat to the environment because you decrease your own surface area.

Those bone-chilling temperatures aren’t all bad news! Find out seven surprising health benefits of cold weather.

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how your body deals with freezing weather - Frost Portrait of a hiker Climber. Wrapped in hat and scarf
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Over time, your brain stops operating on all cylinders

Once your body goes into a hypothermic state—a core temperature that’s too low—your brain and nervous system have a harder time functioning and maintaining normal thought. “There are stories of hunters or people out in the cold, maybe they fell in water or got lost,” Kenefick says. “The hypothalamus tries all the mechanisms that usually work—and then when those fail, it becomes unclear of what to do next. People have been found in freezing temperatures with all their clothes off, because the hypothalamus said, ‘OK, well, let’s try dumping heat out there—making people feel hot—and see if that will work.” If the hypothermia becomes severe enough, the hypothalamus can get really out of whack.

These winter driving mistakes could be putting you in danger.

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how your body deals with freezing weather - Ivory woman gloves in snow with red coat
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Your skin turns white and hard

These are signs of frostbite, a condition when your exposed skin gets too cold and freezes. Cheeks, nose, and fingers tend to be especially vulnerable because they are getting less blood flow because of the vasoconstriction. Also, your fingers are cylinders, which gives them more surface area relative to their size and makes them more vulnerable to heat loss. Frostbite means the skin tissue has become damaged. If it’s severe enough, says Kenefick, it can turn black and actually fall off. At first you will feel pain; as your skin gets colder and colder, it will feel numb. “When this happens, the thermoreceptors in your skin have stopped working,” Giesbrecht says.

Here are the skin changes you should never ignore.

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how your body deals with freezing weather - girl looking into mirror
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Your skin gets rashy and red

Some people have an allergic reaction to cold—but not necessarily freezing—weather, a condition known as cold urticaria or less formally, “winter bumps.” It’s not a reaction to very cold weather, like frostbite, but rather just dry, cool conditions, which can cause an allergic-type reaction in certain people with sensitive skin.

Here’s how to choose the best moisturizer for your skin this winter.

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how your body deals with freezing weather - Winter running Asian girl wearing cold weather clothing for outside exercise in snow storm snowfall during winter training outdoors in city street. Fitness woman exercising.
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You have trouble catching your breath

Normally when you inhale air, your nose helps moisten, humidify, and warm it before it moves down to the lungs. But in some people, like patients with asthma, or in some cases where the weather is just so bitter cold, the air doesn’t warm up enough first, which causes the lungs to spasm and constrict, which makes breathing difficult, says Kenefick.

Take a look back at the worst snowstorms in Canadian history.

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how your body deals with freezing weather - Girl with coffee and mobile phone
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Your muscles go on the fritz

As muscle tissue cools, it doesn’t work as well, says Giesbrecht. “At first, you lose the ability to do fine motor tasks, like using your cell phone correctly,” he says. “Then eventually [as your bigger muscle groups are affected], you might not, say, be able to hold on to an overturned boat in cold waters.”

Next, find out what it could mean if your hands are always cold.

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