Best Cold Weather Mummy Sleeping Bag in 2024

If you’re in a rush and want to find out what the best mummy sleeping bag is, we recommend the Nemo Disco sleeping bag.


For all you car campers out there, how many of you use a rectangular sleeping bag when it’s time to go to bed at night? Probably many of you. They’re comfy, spacious, and can often be zipped together to allow couples to share one giant sleeping bag.

Perhaps you’ve been camping this way for awhile now, and you’ve decided to be a bit more adventurous. Maybe there’s a certain mountain that you’ve always wanted to spend a week exploring, or perhaps camping in the colder months is appealing to you. If that’s the case, you’ll want to find yourself a good cold weather mummy sleeping bag. We’ll cover everything you need to know, and offer a few of our own suggestions, so you’ll be prepared for your next adventure.

Mummy Sleeping Bags At A Glance

If you’re in a hurry, check out this quick list of our favorite mummy bags – otherwise, keep on scrolling to get to the full reviews!

Sleeping Pad

woman in a blue sleeping bag on a gray sleeping pad

When my dad first brought me camping, he wanted to avoid buying a sleeping pad for each of us. They tend to be thin, and somewhat expensive for the amount of cushion that they have, so he thought it was an unnecessary purchase. Thankfully, my mom convinced him to go for it. If she hadn’t, the camping trip would’ve been a lot more unpleasant!

Needless to say, we can’t talk about sleeping bags without mentioning their mandatory counterpart – sleeping pads. For backpacking purposes, I’m a fan of ones that are made out of closed cell foam. They don’t offer as much padding or insulation as some of their relatives, but I love how lightweight and easy to pack away they are. You can also choose some that are inflatable or have thicker foam padding if that’s something you would prefer. Try to find something with a high R-value, as this will provide better insulation between you and the ground.

Important Features

Temperature Rating

inside of a sleeping bag

I think it’s safe to assume that most of us like to be comfortable while we sleep. One of the biggest factors that influences this is the temperature, and your sleeping bag is going to be one of your primary sources of heat. The tent itself is great at blocking wind chill, and insulating against some of the colder, outside temperatures, but ultimately isn’t going to be effective at keeping you warm enough during the night.

Now, this isn’t going to be as important if you’re camping when it’s hot and muggy. In fact, you may even opt to lay down on top of your sleeping bag instead of inside it when the summer heat is weighing down on you! But once the climate starts to cool off, or if you find yourself camping in the mountains, you’ll want to pay more attention to the temperature rating for your sleeping bag, and perhaps even get a sleeping bag liner to go with it.

Most bags come with two numbers:

  • Tested Comfort – the lowest temperature it can be where you’ll still feel relatively comfortable inside your sleeping bag. At this temperature, it won’t feel amazing, but you also won’t experience too much discomfort.
  • Tested Lower Limit – the lowest temperature it can be where you’ll stay safe inside your sleeping bag. You won’t be comfortable at this temperature, but you also won’t freeze to death.

A proper understanding of where you’ll be camping, and what the weather will be like, is necessary for determining what temperature rating you’ll want. Also keep in mind that the tested comfort rating only tells you the coldest temperature you’ll still be somewhat comfortable in. If it’s going to be 40 degrees Fahrenheit outside, you’ll want your tested comfort rating to be about 30 degrees. This will allow you to be truly comfortable during the night.

Fill Type

inner lining of a gray sleeping bag

When it comes to the fill of a sleeping bag, you’ve got two choices: down and synthetic. Each comes with it own pros and cons, but overall, I would argue that down is the (far) superior option.

Taking a look at synthetic, it does have some very noteworthy benefits. Since it’s a manufactured material, it can be produced quickly and cheaply, making synthetic bags more inexpensive than their down counterparts. Synthetics are also unique in their ability to maintain their insulative properties when wet. On the off chance that you fill gets completely soaked, you can still stay warm inside your mummy bag on those chilly nights.

That’s pretty much where the benefits of synthetic end, though. Although down is more expensive and won’t insulate when wet, it’s still the superior option. Not only is it lighter in weight, but you also need less of it to get the same insulative effect. Since less material is needed to stay warm, you can cut back on both weight and bulk.

Backpacking vs Car Camping

woman in a blue sleeping bag lying on the grass

The great thing about mummy bags is that they can be used no matter what you’re doing. There’s no harm in making it your bed while car camping, and they’re the ideal piece of gear for backpacking trips. Rectangular sleeping bags on the other hand? Well, they’re really only useful if you don’t plan on walking long distances with them.

A good backpacking sleeping bag is going to be different from a car camping sleeping bag in a few ways:

  • They’re lightweight and easy to pack down.
  • They have better warmth and insulation, despite there being less material, usually because of the type of insulation used in its construction.

Obviously, there are a few cons as well. They fit snugly, tend to be less comfortable, and don’t give you any room to stretch out or turn over in your sleep. But for the job that they’re meant to do, cold weather mummy bags are worth the tighter squeeze for how easy they are to pack away and how well they keep you warm at night.

Unlike rectangular sleeping bags, mummy bags have a hood that covers over your head to help prevent heat from escaping. So even if you don’t plan on backpacking, mummy bags are essential for cold weather car camping, to ensure that you stay as warm as possible for as long as possible.

Mummy Sleeping Bag Comparison Table

Sleeping Bag Comparison
Sleeping BagsWeight (lbs)Temperature RatingMaterialInsulation
REI Co-op Down Time 252.525°FPolyesterDown
Nemo Forte3.520°FPolyesterSynthetic
Nemo Disco2.614°FNylonDown
Sea to Summit Spark1.518°FNylonDown
Marmot Never Summer40°FNylonDown
Mountain Hardwear Bishop Pass GORE-TEX 152.615°FGORE-TEXDown
Sierra Designs Cloud 201.926°FNylonDown

Top Mummy Sleeping Bags – Reviewed

REI Co-op Down Time 25 Sleeping Bag

Temp. Rating: 25 Degrees

Insulation: Synthetic

Weight: 2.5 Pounds

Compressed Volume (L): 5.7

REI is known for being a popular outfitter for campers, selling brands like Nemo, Marmot, and many other high end products. But sometimes these items overshadow REI’s own exclusive brand, which I have found to be of equal quality (if not better) than many of the other mainstream products out there.

The Down Time sleeping bag is one of these items. It’s a nicely shaped bag that hugs the contours of your body for better heat retention, while still providing enough wiggle room so you don’t feel claustrophobic. I’m a big fan of a large footbox too, since I hate the feeling of my legs and feet being restricted.

The 3 panel hood is great at keeping cold air out, and it even comes with differentiated drawcords (one round, one flat) to help you adjust the head and neck area even when you can’t see what you’re doing. There’s also a full draft tube and face muffler for added warmth. The fill is down, so if it gets wet, it won’t do its job properly, unlike sleeping bags with a synthetic fill. But who said anything about getting wet? There’s a durable water repellent on the outside of the polyester sleeping bag material, allowing you to stay dry even if it’s wet on the outside.

Reasons For

Differentiated drawcords

Waterproof shell

Tested lower limit of 29 degrees

Water resistant fill

Large footbox

Reasons Against

Zippers snag easily

A bit tight in the shoulders

Nemo Forte – Women’s Sleeping Bag

Temp. Rating: 20 Degrees

Insulation: Synthetic

Weight: 3.5 Pounds

Compressed Volume (L): 11.7

When it comes to Nemo, I’m a fan of most of their products. Though they tend to be more on the spendy side of the spectrum, it makes sense given the overall quality of the gear. While the Forte is about twice as expensive as the Trailbreak listed before it, the sleeping bag itself is more developed and home to a variety of fancy features.

For example, there’s more room around the elbows and knees, allowing side sleepers the opportunity to rest in their favorite position. Considering 70% of the population sleeps on their side, and most cold weather mummy bags aren’t big enough to accommodate this, I’d say it’s a pretty useful feature.

Also, if you look at the picture on the right, you may notice the two, light blue vertical slits in the bag. Those are called Thermo Gills, and they allow you to let some of your body heat out of the sleeping bag without letting any drafts come in. That way, you’ll be able to enjoy milder night inside your bag without getting too hot in the process. And trust me, you won’t have any trouble staying warm in here. Nemo realized that women tend to run a little colder than men, so they made sure to pack in the insulation, providing temperature ratings that will easily see you through Spring, Summer, and Fall.

Reasons For

Highly insulated and cozy

Thermo Gills allow customized heat retention

Extra room in the elbows and knees for side sleepers

Waterproof material to withstand tent condensation

Integrated pillow pocket

Reasons Against

Hard to get into its compression sack

Getting the correct size can be a challenge

Nemo Disco Sleeping Bag

Temp. Rating: 14 Degrees

Insulation: Down

Weight: 2.6 Pounds

Compressed Volume (L): 7.2

Though not a “true” mummy bag, Nemo’s Disco sleeping bag still offers high quality warmth and insulation within its semi-rectangular shape. It’s going to be a bit bulkier than many of its counterparts, but there’s a good reason for that. All of the extra insulation puts the tested lower limit on this bag down to 14 degrees, which is low enough for most types of winter camping.

The down fill is incredibly warm and hydrophobic, meaning it won’t soak up water as easily. Considering down loses its insulation ability when wet, this feature is quite useful if you expect to get your bag drenched in water. Even so, it won’t be easy for any kind of liquid to penetrate the nylon shell.

Additionally, the Disco shares quite a few features with the Forte listed above. There’s additional room in the elbow and knee region, making it easier for side sleepers to twist and turn during the night. And the Thermo Gills allow body heat to escape without letting drafts in, so you’ll be able to regulate the internal temperature to your liking. And trust me…you’ll get warm in this sleeping bag. I wouldn’t recommend sleeping inside it during the summer months, but there’s so much insulation that it makes a great bed if you lie on top of it.

Reasons For

Thermo Gills

Lots of extra room to move around

Draft tube

Hydrophobic down fill

Rated for very cold temperatures

Reasons Against

The drawstrings near the head can be uncomfortable

Because there’s a lot of extra space inside, it can take longer for it to warm up

Sea to Summit Spark Sleeping Bag

Temp. Rating: 18 Degrees

Insulation: Down

Weight: 1.5 Pounds

Compressed Volume (L): 4.6

For backpackers especially, the weight of each individual piece of gear is a major consideration. A few extra ounces makes a big difference when you’re trekking with all your belongings on your back, which is why an ultralight sleeping bag is an invaluable resource. The Spark, by Sea to Summit, fits the bill in this regard, weighing in at a mere 12 ounces for the regular size. That’s pretty good, especially since the regular sized Nemo Disco mentioned above weighs 2 pounds 11 ounces!

Of course, it really boils down to what you’re looking for in a sleeping bag. The Spark might be lightweight, but it’s not going to be your best option in colder temperatures. Below freezing, especially, you’ll start to feel pretty uncomfortable. I’d suggest this product for those of you who enjoy long treks during late spring to early fall, and don’t necessarily want to do any mountain camping before May or after September. For how light it is, the fill is shockingly warm, but not enough to be used in more extreme conditions.

Reasons For


Decent heat retention considering how light it is

Vertical chest baffles to prevent the insulation from migrating

Nice mummy contouring for maximum efficiency


Reasons Against

It’s quite tight and the zipper is short, so getting in and out can be a challenge

A little expensive

Marmot Never Summer Sleeping Bag

Temp. Rating: 0 Degrees

Insulation: Down

Weight: 4 Pounds

Compressed Volume (L): 14.2

Never Summer is an interesting name for a sleeping bag, isn’t it? Perhaps you might have guessed it, but this bag actually lives up to its name in the sense that you won’t want to use it in the summer! Rated for temperatures down to 0 degrees (yes, you read that right), Marmot put a lot of effort into this cold weather product. And in the process, they made it practically unusable in temperatures above 60 degrees, simply because of how hot it gets inside.

But generally speaking, you’re probably not getting a cold weather mummy bag because you plan on using it in the summer. And if you want one for backpacking, grab the Spark by Sea to Summit listed above – this “Never Summer” bag is too heavy for backpacking purposes, unless you’re going in the colder months. At just over 3 pounds, you’ll definitely feel it in your pack.

The duck down is what’s taking up a lot of that weight, though, and is something you’ll be happy to have when temperatures drop below freezing. And if the wraparound footbox and multi-baffle hood aren’t enough to keep you warm, there are a couple of pockets inside the bag where you can stuff hand warmers.

Reasons For

Really warm

Internal stash pocket

Nylon shell with water repellent finish

Extra short zipper on the right side that makes it easy to access the hood

Reasons Against


Snagging zippers

Mountain Hardwear Bishop Pass GORE-TEX 15 Sleeping Bag

Temp. Rating: 15 Degrees

Insulation: Down

Weight: 2.6 Pounds

Compressed Volume (L): 10.5

This variation of the Mountain Hardwear Bishop Pass is a bit of an anomaly in the sleeping bag world. That’s because the shell is made from Gore-Tex, instead of regular nylon, which is incredibly windproof. I wouldn’t go as far as saying that it’s 100% waterproof, but it is very water resistant. Which is to say, you could get caught in a light rain shower without a shelter and still be dry inside.

Why is this so important? Well, the Bishop Pass is a mummy bag rated for 15 degree weather. That’s pretty cold, by most standards, and when you’re camping in high humidity locations when it’s that chilly outside, condensation will accumulate quickly. Your average sleeping bag will get soaked in this type of environment, once that condensation starts to fall on you. If your shell isn’t very water resistant, all of that moisture will seep into your insulation, which can be a problem if you’re using down. And even if you aren’t using down, it’s not like it’s fun to pack up a wet sleeping bag.

Really, the Bishop Pass is great for a select group of people. Cowboy campers, hammock campers, and those who expect heavy condensation will benefit the most. Overall, it feels very spacious on the inside, and the down fill has a good amount of loft. The included compression sack is also very effective, squeezing this bag down to 10.5 liters when packed.

If you don’t think you’ll need the Gore-Tex, it’s possible to find lighter sleeping bags with similar specs. However, if you want that wind and water protection, the Bishop Pass is the way to go.

Reasons For

Made using Gore-Tex



Fairly spacious

Good compressed size

Reasons Against

Made for a select group of people

Sierra Designs Cloud 20 Sleeping Bag

Temp. Rating: 26 Degrees

Insulation: Down

Weight: 1.9 Pounds

Compressed Volume (L): N/A

Love it or hate it, there’s no denying that the Sierra Designs Cloud 20 is a unique sleeping bag. I happen to love it, but I know that the zipperless style isn’t for everyone. Even so, if you find yourself getting tangled up in your bag during the night, this might be the design that you need to help you get out in the morning.

You can probably tell just by looking at the photo, but the Cloud wraps into itself like a robe. Because of that, I would say that it doesn’t trap heat quite as well as a zippered bag, but that won’t matter too much with the Cloud. It’s already a pretty warm bag to spend the night in, rated for comfort down to 26 degrees (for women). The tested lower limit (for men) drops even more, coming in at 15 degrees.

Because of the high loft, down fill, not only do you get great heat retention, but you also get a comfortable amount of fluff to lie on. Another benefit is that it’s one of the lightest bags in our review, and it packs down pretty small as well. The zipperless design also gives you more wiggle room, allowing the chest area to expand enough for side sleepers to find a good position without feeling constricted. And considering how inexpensive it is, it’s not hard to see why the Cloud is one of my favorite mummy bags.

Reasons For


Packs down well

Great for side sleepers



Reasons Against

The down likes to shift around a bit

Why Trust US

At Untamed Space, we’re passionate about helping you have the best camping experience possible. Our team of experts have experience camping and backpacking all over the world, allowing them to provide insightful and relevant content to guide you in your outdoor pursuits.

All of our reviews are based on a combination of firsthand experience, extensive research, and an analysis of customer feedback. We are an independent website and do not receive payments or incentives from manufacturers to promote their products, and we continuously update our content to provide new information based on product availability. Wherever you are in your journey, whatever gear you’re searching for, you can be sure to find unbiased and up-to-date reviews for all of your needs.


Is Down or Synthetic a Better Fill Material?

Both down and synthetic fill materials have their advantages when it comes to mummy-style sleeping bags. Down insulation offers excellent warmth-to-weight ratio and exceptional compressibility, making it ideal for backpackers and those needing a highly packable sleeping bag. However, it’s important to note that down loses its insulating properties when wet, so it may not be the best choice for wet or humid environments.

Synthetic fill, on the other hand, retains insulation even when damp and dries quickly, making it a reliable option for unpredictable weather conditions. It’s also often more affordable than down. Consider your specific needs and the expected weather conditions to determine which fill material is the best fit for your mummy sleeping bag.

Are Mummy Bags Suitable for Taller Individuals?

How Important is Packability in a Mummy Sleeping Bag?

Final Thoughts

Cold weather mummy bags are the ideal sleeping space for extreme campers. They’re well insulated, lightweight, and tend to pack down well, so you can tackle long hikes and cold temperatures with ease. From an overall versatility standpoint, our favorite mummy bag is the Nemo Disco because of its temperature rating, comfort level, and other handy features.

Though not designed for winter camping, you can certainly get away with using it late into year. It’s puffy and warm, but not unbearably snug like many mummy bags can be, since it has extra room in the elbows and knees. And if it gets too hot on those milder nights, just open up those Thermo Gills to let some heat escape without worrying about a draft coming in.

Meet the Author!

By the age of 20, Spencer had already tackled some of the most famed mountain ranges in Europe, Asia, and North America. His mission is to help others accomplish their own outdoor-related goals, even within the time constraints of a 9-5 job and a busy life schedule.

Leave a Comment

Your email address will not be published. Required fields are marked *