How to stay warm while sleeping in the frigid outdoors

Dry socks may be the most important thing you pack.

This post has been updated. It was originally published on 02/12/2021.

Frozen toes at the bottom of your sleeping bag, the fear of frostbite looming in the back of your mind, and the ever-present possibility that you didn’t bring enough layers.

A fear of nights spent outdoors in below-freezing temperatures is enough to deter even the most passionate campers from spending a night in the wild in wintertime. After all, no one likes to wait for the sun to rise as they shiver.

“People hear ‘winter’ and they think ‘impossible.’ But if you have the right systems and the right gear, it can be comfortable and fun,” says Katie Oram, a winter field instructor at the National Outdoors Leadership School, who routinely spends 10 to 18 days at a time in often snowy, wintery backcountry conditions.

Learning how to beat that unforgiving chill and stay warm and cozy will allow you to have the full winter wonderland experience, plus take advantage of the empty trails, quiet animal encounters, and the beautiful silent nights.

Get the right equipment

First things first: make sure your camping gear can handle the cold, whether you’re sleeping in the backcountry or at a developed campsite. While an ultralight tent and lightweight sleeping bag will do in spring, you are guaranteed to have an unpleasant night if you set out during the colder months without items specifically designed for winter.

And if you’re not sleeping, you’ll be exhausted, which means you’re not going to have fun.

Start with a tent that’s rated for 3.5 or four seasons, which will often feature heavier fabrics, few vents, and a rain fly that extends all the way to the ground. They are designed to trap heat in and keep snow from collapsing your structure, making them much warmer and more suitable for winter climates than typical three-season tents.

Related: How to avoid (and treat) hypothermia

Next, check local weather forecasts and make sure your sleeping bag is rated at or below the overnight temperatures you’re expecting. Keep in mind, though, that rating parameters may differ from brand to brand. Some refer to the temps at which you can sleep comfortably, while others to the lowest possible temperature at which an average person will feel comfortable.

Also, men’s and women’s bags are rated differently as women typically sleep cold. If you’re a woman with a men’s or unisex bag, it might not be good for the temperature you think it is. Check the tags or manufacturers’ website for more details about your specific bag.

If you don’t think your bag can hack it on its own, slip it inside another bag, or use a sleeping bag liner for a double layer of warmth. Some models can raise your bag rating by as much as 30 degrees Fahrenheit, while battery-powered pads and liners can keep you even cozier.

Finally, don’t neglect your sleeping pad—it keeps you off the cold ground, which can suck heat from your body, so it’s just as important as your bag. Start with an insulated, inflatable pad, and consider layering it with a closed-cell foam pad for extra warmth. Just make sure the pads are at least as long as you are tall (feet hanging off the end leave your toes vulnerable), and place the one with the highest insulation rating (R-value) closest to your body.

Layer up

People hiking in a snowy mountain
Keeping your gear dry is key. Whether it’s water, snow, or sweat, avoid excess moisture at all costs. Graziano De Maio / Unsplash

Especially in winter, the outdoors is all about layers—that also goes for when you’re inside your sleeping bag.

Start with a warm base layer that’s comfortably snug and close to your skin. Synthetic fabrics or wool will do nicely. Outdoors people say cotton kills, and that goes double in winter, so stay away from it. If cotton or hemp garments get wet from snow, rain, or even sweat, they can make your body temperature drop dramatically, and take too long to dry.

[Related: Winter camping is a great way to see more nature and fewer people]

A base layer, together with a warm hat, a pair of gloves, a neck gaiter, and one or two pairs of socks may be enough for warmer sleepers. But if you’re still cold, Oram suggests adding another layer or two, like a fleece sweater or pants. Top it all off with a light puffy jacket for extra warmth if necessary, and you’ll be good to go. The key is to go for three layers or less, as more will prevent your body from heating up the space inside the bag and keep you warm.

And if after all of this you’re still chilly, drape your puffy coat or a jacket on top of your sleeping bag like a blanket.

Tips for sleeping cozy

Before you even climb into your sleeping bag, prepare yourself by getting your body moving.

“You’ll get warmer faster and stay that way for longer if you’re already somewhat warm before you get in your sleeping bag,” Oram points out.

The point isn’t to break a sweat—remember: damp layers will make it harder to stay warm—but to raise your body temperature enough so that when you hit the hay, you’re already nice and toasty. Shoveling snow around your campsite or doing some good ol’ pushups or jumping jacks will do the trick.

Next, don’t underestimate the power of hand and foot warmers. There are many options available, from single-use disposable sachets to rechargeable battery-operated foot and hand warmers. Hold them to keep your hands warm, place them at the bottom of your bag to heat your feet, or stuff them into a chest pocket to warm your core.

You can give your sleeping bag a head start by making your own warmer too. Oram suggests heating a pot of water to near boiling, pouring it into a non-insulated, hard-sided bottle like a Nalgene, and placing it in your sleeping bag before you get in. Just make sure the cap is on tight so it doesn’t leak, and that the bottle is not hot enough to burn you.

“When I go to bed, that can be a total game-changer for me,” Oram says, noting that she will often fill up two bottles: one for her core, and the other for her feet.

Related: How to build a fire in the wilderness

Another tip is to treat yourself to a hot, carbohydrate-heavy meal, or high-calorie snack or beverage before you turn in. This will warm you from the inside out and start your body’s natural digestion engine to keep you warmer throughout the night.

If you’re not camping solo, you can also take advantage of a camping partner to keep you both warm. Use a two-person sleeping bag or zip two bags together so you can get cozy. In this setup, wearing fewer layers will make sharing that body heat more efficient.

Finally, if you’ve heard about not holding your pee to keep warm at night, think again. This notion comes from the belief that your body expends precious energy in maintaining your bladder’s content at body temperature, but this is simply not true.

“Your body does not expend more energy to keep urine warm since it is already at body temperature,” says Dr. Ladin Yurteri-Kaplan, a urologist at Columbia University Medical Center.

Exposing your skin to the cool air might give you a chill, but going or not going won’t make a difference when it comes to surviving the frigid cold. Regularly holding it is not the healthiest or most pleasant choice, though, so when nature calls, make sure to answer.

Keep those toes warm

Your extremities might be the most important parts of your body to care for and pay attention to as you seek to prevent discomfort and cold injuries such as frostbite.

Sleeping in damp clothing is always a bad idea, but this is especially true when it comes to socks. Tucking in with wet feet can cause frostbite or injury called immersion or trench foot, caused by prolonged exposure to wet and cold conditions that—worst-case scenario—can cause skin tissue to die.

“One pair of dry socks lives in my sleeping bag,” Oram says.

Empty space in your bag means more space that your body has to heat up, so if there’s too much of it, fill it. For this, use extra clothing layers like puffy jackets, fleece zip-ups, and spare socks, and concentrate them around your feet. Don’t forget to make sure they’re all dry.

Alisha McDarris

Alisha McDarrisis a freelance writer for PopSci and specializes in all things outdoorsy and sustainable. She’s also written for Backpacker, Outside, BBC Travel, and more, plus she's the co-founder, head honcho, writer, photographer, and on-screen personality of sustainable travel and adventure blog Terradrift. When she’s not writing, you’ll find her backpacking, kayaking, hiking, or rock climbing, all while attempting to determine how many times she can wear a hiking shirt before her husband begs her to wash it.