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The best sleeping bags are designed to keep you warm in the coldest temperatures while being flexible enough to allow you to stay cool when temperatures rise. If you can find a sleeping bag that does both of these things, you’ll save money by not having to buy more than one.
Depending upon where you live and how long you extend your camping season, you’ll want to consider owning a sub-zero sleeping bag. To help you in your search, we’ve selected the top five cold weather bags we could find based on several criteria. But before we get to our list, let’s take a look at the most important features of sub-zero sleeping bags.
Sleeping Bag Temperature Ratings Explained
When buying a sleeping bag, it can be difficult to make sense of how the temperature ratings work. One of the problems is that temperature ratings are not an exact science. For example, a comfort or lower limit temperature rating that’s established in a lab is purely an estimation – it cannot predict an individual’s comfort level at a specific temperature, the type of clothes they’re wearing, where the sleeping bag is located, or the surrounding environmental conditions.
A warm sleeping bag liner can also improve a sleeping bag’s temperature rating. With these things in mind, there are some guidelines you can follow that will help you find a sleeping bag that’s suitable for the conditions you prefer to sleep in.
Standardized Temperature Ratings
A sleeping bag might have one of two standardized temperature ratings assigned to it: ISO 23537 or EN 13537. While the certification doesn’t guarantee that you’ll have the same results with the bag as they did in the lab, you should be able to make an accurate comparison amongst, say, ISO-rated sleeping bags because they were all tested in identical conditions.
Not all sleeping bag manufacturers will use the ISO or EN ratings, as they won’t deem them necessary for a bag designed for summer camping. They likely won’t appear on extreme temperature bags either. Regardless of the standard being used, it’s best to consider all temperature ratings to be an estimate.
Comfort Rating vs. Lower Limit Rating
A comfort rating suggests a temperature at which a cold sleeper will still be comfortable. Because studies show that women tend to feel colder when sleeping earlier than men, comfort ratings are assigned to women’s sleeping bags. Men’s sleeping bags are assigned a lower-limit rating, which assigns a temperature above which a warm sleeper should feel comfortable. For example, a sleeping bag with a comfort rating of 30℉ might have a limit rating of 20℉.
What Is an Extreme Temperature Rating?
An Extreme temperature is the third rating and indicates a temperature at which the sleeper may feel cold, but they will survive the night. Not all sub-zero sleeping bags will have an extreme temperature rating, but hard-core cold-weather campers and backpackers should use this rating to find the warmest bag possible.
Other Factors to Consider When Purchasing a Sub-Zero Sleeping Bag
When looking for a sleeping bag that will keep you warm in various conditions, there are other key considerations aside from the temperature rating. Here is a list of other important features for your next sleeping bag.
Sleeping bags come in two main shapes: rectangular and mummy. Each one has its pros and cons. Rectangular sleeping bags have more room inside the bag, so it’s easier to feel comfortable. On the downside, they require more material, making them heavier and more difficult to pack and transport.
Mummy bags are warmer and lighter, making them ideal for backpacking, but with less room inside, they are less comfortable than rectangular bags. However, I tend to be a bit claustrophobic, so I’ll give up some added weight and opt for the rectangular sleeping bag.
2. Insulation Type
Most sleeping bags use either polyester (synthetic) or down feathers for insulation. Down feathers can come from a duck or a goose. Each type of sleeping bag insulation has its advantages.
Synthetic Sleeping Bag
Synthetic sleeping bags are generally less expensive, but that doesn’t mean they don’t perform as well. In fact, they are better for wetter conditions than down-filled sleeping bags because they dry more quickly. They’re also non-allergenic, something that many campers will find important.
Down-Filled Sleeping Bag
Down sleeping bags are more expensive, but they offer more warmth at a lighter weight. Chances are, the best lightweight sub-zero sleeping bag will be down-filled. They are also ideal for dry conditions.
Depending on the type of camping you’re doing, the weight of your sleeping bag can be an important factor. The sleeping bag shape (mummy vs. rectangular) and material can affect the weight. Backpackers will definitely want to choose a lighter, more compact sleeping bag. On the other hand, if you have plenty of storage and don’t need to walk far to your campsite, weight is less of a worry.
4. Zipper Location/Ergonomics
Far from being an after-thought in sleeping bag design, zippers contribute to the overall insulation level and the quality and ergonomics of any sleeping bag. In addition, a heavier, more durable zipper should last much longer than a flimsy zipper made from a cheaper material.
The longer the zipper, the more opportunity for cold air to get into your sleeping bag. Zippers are a bit like the windows on your home. They are weak insulators because they let cold air in and warm air escape. This is why most mummy sleeping bags have shorter zippers.
But a shorter zipper can make your sleeping bag less desirable when temperatures rise because you can’t open up the bag as much to cool off while sleeping. So you’ll want to give some thought to the zipper location before choosing a sleeping bag.
The Best Sub-Zero Sleeping Bags for Cold Weather Sleeping
Now that you have a better understanding of what to look for in a cold-weather sleeping bag, here are 5 top-notch sleeping bags that fit the bill. I’ve been careful to select different styles and price points to make it easier to find a sleeping bag that’s well suited for you.
1. Hyke & Byke Snowmass Zero Degree Down Sleeping Bag
This premium down-filled sleeping bag from Hyke & Byke is perfect for backpacking in any season. It has a 20℉ temperature rating, which means that it should keep you warm when the thermometer drops below freezing. Unsurprisingly, it’s a mummy-shaped bag and is super lightweight at only 3.75 lbs. It comes in three lengths (short, regular, and long) to accommodate sleepers from 5’6″ all the way to 6’6″ tall. Lastly, this sleeping bag is equipped with 2 YKK zippers, renowned for their quality construction and durability.
- Down-filled, 4-Season mummy sleeping bag
- Temperature Rating 20℉
- Lightweight at under 4 lbs
- Available in 3 sizes (Short, regular, long)
- Moisture resistant
- Heavy-duty, YKK zippers
2. TETON Sports Celsius XL Sleeping Bag
The Teton Sports Celsius XL Sleeping Bag is built for extreme conditions. It comes with a temperature rating of -25℉ (-32℃), and while I’m not sure if that is accurate, it’s certainly made for all four seasons. Unlike the lightweight Hyke & Byke bag, this one tips the scales at just under 10 lbs (4.3kg). It’s rectangular in shape, so while it will offer more comfort than a mummy bag, it will require more effort to pack up and transport. If you’re using this sleeping bag in warmer temperatures, you have the option of unzipping it all the way to the bottom so that you can keep cool on those warm summer nights.
- Made of synthetic fiber-fill
- Temperature rating -25℉ (-32℃)
- Weight 9.5lbs (4.3kg)
- Rectangular shape
- Available in left or right zip
- Unzips to bottom
- Half circle mummy hood
- Padded shoulder area prevents drafts
3. Coleman Brazos Cold Weather Sleeping Bag
Price can be a factor with sub-zero sleeping bags, as they are often a costly investment. However, that’s what makes the Coleman Brazos cold weather sleeping bag a great choice for campers on a budget. It’s made from a synthetic polyester fill and comes with a limit rating of 20℉ and a comfort rating of 40℉. In other words, it’s a 3-4 season sleeping bag, depending on where you live. The bag is rectangular in shape, is reasonably light at just over 5lbs, and features a heavy-duty zipper. If there’s a drawback, it’s that at 75″ long, it’s not ideal for taller people (over 6 ft).
- Synthetic polyester fill, 3-4 season mummy bag
- Temperature Rating (Comfort 40℉/Limit 20℉)
- 5.4 lbs
- 75″ length
- Does not include hood
- Rugged zipper
4. Active Era Mummy Sleeping Bag
The Active Era Mummy sleeping bag shares many similarities with the 1st bag on our list, in that it’s a mummy-style, super lightweight (3.3lbs), and has a robust temperature rating of 15℉. In addition, I like that it has an attached hood and is plenty long (87″), enough to accommodate even the tallest camper.
- Cotton Jersey fill, 3-4 season mummy bag
- Temperature Rating 15℉
- 87″ long w/hood
- Includes a compression sack
- Heavy-duty zipper, internal pocket for keys or cell phone
5. Browning Camping McKinley Sleeping Bag
The McKinley sub-zero sleeping bag from Browning Camping might be the most uniquely shaped sleeping bag on our list. The main body of the bag is rectangular, while the hood is tapered much like the hood on a mummy sleeping bag. At a whopping 90 inches in length, it’s easily the largest sleeping bag on our list, long enough to accommodate the tallest of sleepers. But, of course, its large size means that it’s also quite heavy, at over 12 lbs. For this reason, it’s not recommended for backpacking. The temperature rating (comfort) is 30℉ (0℃), but based on the product reviews, this extreme weather sleeping bag will keep you warm as temperatures dip well below freezing.
- Synthetic Fill, 4-season bag
- Comfort rating 30℉ (0℃)
- Dimensions 36″ X 90″
- Weight 5.5kg (12 lbs)
- Not suitable for backpacking due to size and weight
Which Sub-Zero Sleeping Bag Is the Best?
There you have it, our list of the top 5 sub-zero sleeping bags that you can buy today. Only you can decide which one is the best because it depends on what you’re looking for in sleeping bags rated below zero. Aside from the temperature rating, size and weight are important considerations, as is the type of insulation and the price. If you’re looking for the best value, the Coleman Brazos cold weather sleeping bag would be a good choice, while the Hyke & Byke or Active Era bags will appeal to backpackers.
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