If you camp in the dead of winter or in extreme environments like the Himalayas, the best cold weather sleeping bags are a necessity when temperatures dip below freezing. As you settle in to sleep after a hard day on the trail (or glacier), you’ll appreciate their lofty warmth and much needed coziness. And while a good sleeping bag can make or break your sleep experience, they’re not the only factor. “A huge part of staying warm at night comes down to your entire sleep system,” explains Porter McMichael, the assistant operations manager and guide at the International Mountain Guides, “which includes your sleeping pad and tent, too.”

The best cold weather sleeping bags will provide warmth for winter camping and high mountain ... [+] expeditions. Picnic Blankets

Cold weather sleeping bags come in many varieties, from down-filled, which is light and warm, to synthetic, which is bulky but water-resistant. However, the main question to consider is what temperature rating you need. While sleeping bags ship with the brand’s estimated temperature rating, there’s a lot of variability in comfort level. (For example, the Kelty 0-degree bag has a comfort rating of 17 degrees while the Marmot 0-degree bag is comfortable at -3 degrees.)

That’s why many (but not all) bags are externally tested to verify their temperature rating. “EN[or ISO] gives you three standardized ratings based on the actual insulated properties—comfort rating, lower limit and extreme,” explains McMichael. “If a sleeping bag has been EN tested, you’ll be able to compare a Mountain Hardwear to a Marmot.” We’ve included a comfort rating for each of the products below, which indicates the temperature that the average sleeper could rest comfortably—without shivering—in the prone position in a bag.

With this information in mind, read on for the best cold weather sleeping bags so you can sleep outside even when the mercury falls.

Weight: 3.43 pounds | Insulation: 650-fill down | Comfort Rating: -3.2 degrees Fahrenheit

This ultra-lofty cold-weather sleeping bag feels like cuddling up in a cloud. Over the years, this bag has become my go-to option for everything from spring mountaineering trips in the North Cascades to early season backpacking in Olympic National Park to winter car camping in the Rockies.

It’s ideal for both backpacking and car camping because it’s spacious and fluffy, but it also packs down for an overnight trip at a moment’s notice. The hood design is roomy and cozy without suffocating your face (like some mummy bags), and the bottom unzips to provide more space for your feet to move around. This bag is also versatile—when the temperatures rise, you can partially unzip both sides to use it like a blanket rather than an enclosed sleeping bag.

Weight: 4.56 pounds | Insulation: 550-fill down | Comfort Rating: 17 degrees Fahrenheit

For car campers and occasional backpackers who don’t care about weight, this is a great value sleeping bag for the price. It adopts features found on more expensive bags, like an ISO rating and a well-designed collar to keep out drafts and bitter cold. But what I love most about this bag is the material—it’s softer than any sleeping bag I’ve tried and feels wonderful against your skin when the time comes to cozy up.

While this bag is great for most vehicular adventures, it’s not as good for human-powered travel. Its pack size is large, and it’s at least a pound heavier than comparable models, so I don’t recommend fixing it to your pack unless absolutely necessary.

Weight: 2.56 pounds | Insulation: 800-fill hydrophobic down | Comfort Rating: 14 degrees Fahrenheit

Whether you’re backpacking in the rainy Pacific Northwest or ski touring in the Northeast, this cold weather sleeping bag is a great companion for all your adventures. It packs down small enough to fit in any pack and weighs about two-and-a-half pounds. The back of the bag features straps that you can attach to your sleeping pad so it doesn’t shift as you sleep.

It comes as no surprise that Therm-a-Rest uses top notch materials to create this bag. The 100% recycled nylon shell is lightweight yet durable, and the hydrophobic down is suitable for all weather conditions because of it’s moisture-wicking, fast-drying capabilities.

Weight: 2.87 pounds | Insulation: 750-fill UltraDry down | Comfort Rating: 15 degrees Fahrenheit

Mummy bags are widely considered a backpacking staple because they feature excellent thermal retention but if you’re a restless sleeper that tosses and turns, you probably understand the drawbacks of a bag that locks you in place. For those in need of a little more room to move in the middle of the night, the Sea to Summit Ascent is the solution. It’s similar enough to a mummy bag such that it will hold in body heat, but it’s also roomy and rectangular enough that you can sleep on your side without worry.

It has other impressive features, too: the zipper system allows you to easily dump unwanted heat if you sleep hot and the hood cinches down to keep heat in if you run cold. For those that wish to stay connected to the real world, an internal stash pocket is big enough for a phone (which is also important in freezing temps!).

Weight: 3.87 pounds | Insulation: 900-fill down | Comfort Rating: -25 degrees Fahrenheit

Serious trips to places known for cold weather require a sleeping bag that retains warmth like no other. That’s why McMichael directs clients to the EX Peregrine -25 when they’re looking for the best expedition bag. “Until you know how each company does their warmth ratings, its hard to look at a bag and know exactly how warm it will be,” he says, “but this -25 degree bag is probably similar to other companies’ -40s.”

This sleeping bag has everything you need for an extended backpacking trip or full-on Arctic expedition. It’s wide and spacious in case you need to sleep in insulating layers, like puffy pants and a parka as McMichael does in the coldest climates. It features a draft tube along the zipper to prevent air from leaking in. And the shell is water-resistant to prevent your bag from getting wet as a result of morning condensation.

Weight: 2.56 pounds | Insulation: 850-fill down | Comfort Rating: 12 degrees Fahrenheit

It’s almost hard to find a bad review about the Mountain Hardwear Phantom 0; this bag has a cult following for being one of the warmest and lightest bags for its temperature rating. It’s ideal for backpackers, alpine climbers and mountaineers who are focused on weight and warmth. It also comes with its own compression sack so you can get it down to the smallest packed size possible (although we don’t recommend storing it in the compression sack for long periods of time).

The 850-fill down creates a super lofty bag and the water-repellent finish prevents water from beading up on the shell as you sleep. However, the slim mummy shape is incredibly snug and not ideal for those with broad shoulders or wide hips.

Weight: 3.87 pounds | Insulation: 800-fill down | Comfort Rating: -29 degrees Fahrenheit

Just to reiterate: a -20 degree bag will be overkill for most casual winter campers. But if you intend to venture into harsh, wet conditions, your sleeping bag choice matters. “When you’re sleeping in temperatures like -20, the inside of your tent will be covered with a thick layer of frost in the morning,” explains McMichael. “and if you’re somewhere like Denali that gets cold at night and warm during the day, then it’ll frost and then melt and your sleeping bag will get very wet even if the air temperature doesn’t approach freezing.” That’s why low-temp bags, like the Nemo Sonic, come with hydrophobic down and a waterproof coating that’s thicker than traditional 0-degree bags.

But the Sonic takes it a step further, too. The toe box is designed to retain warmth and act as a waterproof barrier so you can dry clothing inside your sleeping bag. It also features Thermo Gills that vent heat without risking cold exposure, and a stretchy design allows you to roll onto your side while minimizing the bag’s footprint. If you don’t need the low temperature rating, Nemo also makes this bag in a 0-degree version.

Weight: 5.7 pounds| Insulation: Synthetic | Comfort Rating: 14 degrees Fahrenheit

Down bags are expensive, and if you don’t need their superior packability, they may not be worth the price point. Synthetic bags, like the Stoic Groundwork, are much more affordable and retain their warmth even in wet conditions. But synthetic definitely has its drawbacks: it’s much heavier and not very packable, for starters. It also doesn’t have as much lofty softness, which is what makes you feel like you’re sleeping in a cloud in a down bag.

However, for an all-around bag for car camping, this cold weather bag is a solid option that will keep you warm when the temperatures dip below freezing. And it’s available for a fraction of the price of down.

Here are a few key factors to consider when shopping for a cold weather sleeping bag:

For anyone venturing into the backcountry or going on a multi-day expedition, a down cold weather sleeping bag will offer superior properties. Down bags are warm and lightweight yet generally more expensive than synthetic alternatives. “I find down to be more comfortable as well—the way it falls and its softness,” says McMichael. “It’s a comfy material.” Down’s major downfall, so to speak, is that it doesn’t stay warm when wet, so it’s important to keep it dry and protected from the elements.

Synthetic bags will be much bulkier—especially with low temperature ratings—so they’re not a great choice if you need to carry your gear on your back. If you choose a synthetic bag, it’s best to stick with car camping. However, synthetic materials retain their warmth when wet, so that gets them bonus points.

A sleeping bag’s temperature rating is an important consideration for cold weather. You have two main options: a 0-degree bag, or a lower temperature bag like -20 or -40. A 0-degree bag will be a good all-around cold weather option that you can use in the midst of shoulder season, as well. It provides decent warmth in a more packable format. “A 0-degree is a really versatile bag because it will keep you warm pretty much anywhere and won’t be massive, heavy and annoying to carry,” says McMichael.

For extreme environments, you’ll want a -20 or -40 degree bag. “What I tend to see is that most males are fine with a -20 [bag] in the coldest places on earth—Antarctica, Everest, Denali, whereas females tend to sleep colder,” explains McMichael. “This is certainly not always true, but anyone who tends to sleep cold prefers a -40 in those situations.”

“One technology that we see really with only -20 and -40 bags is a waterproof or nearly-waterproof outer shell,” explains McMichael. This shell protects you from the melt-freeze cycle of condensation that builds up in the tent in these freezing temps.

The shape of a sleeping bag is also worth considering. Mummy bags, which start wide at the top and taper at the bottom, will provide the most warmth. However, some find them claustrophobic and uncomfortable—especially people who move a lot in their sleep. In that case, a more rectangular sleeping bag like the Sea to Summit Ascent will provide extra room around the hips and legs, but may not retain as much warmth.

Down sleeping bags are best for cold weather because they provide excellent warmth while also being packable. The alternative is synthetic, but McMichael explains that “the warmth-to-weight ratio for synthetic is not very good, and that’s the primary thing you’re after in cold weather bags.”

The lowest temperature sleeping bags available offer protection in -20 and -40 degrees Fahrenheit conditions. McMichael explains that while there is a huge difference between a 0-degree bag and a -20-degree bag, “the difference between -20 and -40 is not big at all,” he says. “It’s pretty much the same sleeping bag, the -40 degree model is just better suited for colder sleepers.” While you may see some bags marketed as -60 degree bags, like the Feathered Friends Snowy Owl EX, this is uncommon and not externally tested.

I am a staff writer at Forbes covering retail. I have been at Forbes since 2013, first on the markets and investing team and then on the billionaires team. In the course of my reporting, I have interviewed the father of Indian gambling, the first female billionaire to enter the space race and the immigrant founder of one of the nation’s most secretive financial upstarts. My work has also appeared in Money Magazine and CNNMoney.com. Tips or story ideas? Email me at ldebter@forbes.com.

I am a staff writer at Forbes covering retail. I have been at Forbes since 2013, first on the markets and investing team and then on the billionaires team. In the course of my reporting, I have interviewed the father of Indian gambling, the first female billionaire to enter the space race and the immigrant founder of one of the nation’s most secretive financial upstarts. My work has also appeared in Money Magazine and CNNMoney.com. Tips or story ideas? Email me at ldebter@forbes.com.

New England raised and New York-based, I'm a twenty-something editor with a penchant for gear. Upon receiving a degree from the University of Massachusetts, I packed my car on a whim and made for the west coast. Like a rebel without a cause, I drove until I found myself in Oregon, a place where towering pines and peaks looked nothing like the old forests back home. It's here that I began my career as a freelance writer, contributing gear-related stories to REI Co-op, Backpacker, GearJunkie, Field Mag and others. Years later, I began working as a copywriter for Backcountry.com before bigger gear-related opportunities lured me back east. 

A jack-of-all-trades, master-of-none type, I've made a few wonderful memories between then and now. I've surfed the frigid waters of the Oregon coast (thanks, wetsuits!), stumbled my way through the Sierras, skied the Canadian Rockies (just barely) and drove across the country a few times (because flying is kinda overrated). These days, I'm messing about with films cameras, appreciating long drives in my old 4Runner and jumping at every chance I get to see something new. 

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I'm a writer specializing in the outdoors and travel. I splits my time between Alaska and Colorado, where when I'm not writing, I spend my time camping, hiking, fishing, and snowboarding (often with dogs in tow). My byline can also be found in The New York Times, National Geographic, The Washington Post, The Guardian, Conde Nast Traveler, Travel + Leisure, and beyond. Connect with me on Instagram (@byebaileyberg) and Twitter (@baileybergs).

I’m a senior fashion editor covering women's and men's fashion, grooming and accessories. My work often explores the unique people and cultural trends that bring products to life and make them worthy of obsession. I grew up in New England and studied art history and architecture at Brown University. My writing has appeared in T: The New York Times Style Magazine, Vogue and the Wall Street Journal, and I’m the author of two books on beauty, including Be Well: New Spa and Bath Culture and The New Beauty: A Modern Look at Beauty, Culture and Fashion. Follow me @Kari_Molvar  

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With an obsession for almost any gadget he's laid eyes on since his hands were big enough to hold them, Quentyn Kennemer has found himself embroiled in the world of technology from the earliest days. Using them as an escape to a better life, he turned to mobile phones to help him access knowledge and opportunities that were otherwise inaccessible to many in his community.

For over a decade now, Quentyn has parlayed his passion into a profession that doesn't feel like work, but instead a constant fulfillment of an undying need to try out all the weird, funky and new innovations he can. When he's not putting digital ink to an LCD, you can find Quentyn getting lost in his favorite video games (literally and figuratively), reading and practicing as an aspiring photographer.

I am a freelance writer specializing in general wellness, relationships, home, and lifestyle trends, with work appearing in Women’s Health, Prevention, Health, Yahoo Life, and more. I have a master’s degree from American University, live by the beach, and hope to own a teacup pig and taco truck one day.

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I am a freelance writer specializing in general wellness, relationships, home, and lifestyle trends, with work appearing in Women’s Health, Prevention, Health, Yahoo Life, and more. I have a master’s degree from American University, live by the beach, and hope to own a teacup pig and taco truck one day.

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As a shopping editor, I always have my eye on the latest deals. When I'm not scrolling through the most recent Anthropologie sale, I'm probably testing out a new serum or a pair of running sneakers for a potential review.

Backpack I'm also passionate about mental health and I've written extensively on the subject over the past four years. In my spare time, I enjoy doing yoga, playing with my shih tzu puppy and creating paintings for my art business, Paint By Kara.