Winter Sleeping Bags

How to Choose a Sleeping Bag for Pacific Northwest Winter Backpacking

If you are used to camping in summer and the shoulder seasons and are wondering what type of sleeping bag you’ll need for winter use in the Cascade Mountains in Oregon and Washington State, here are some basic points to consider.

I don’t represent any brands. I haven’t received any sponsorship or free sleeping bag gear from any companies. These are my independent opinions.

Picking the Temperature Rating

The first thing you need to do is to determine the temperature rating you need. That is, before purchasing a sleeping bag, you want to determine what temperature rating you need for the conditions and months you plan to be outdoors.

Winters in the Pacific Northwest are mild compared to other regions this far north. One way to determine likely temperatures is to study the average temperatures at different elevations on major peaks throughout the Cascade range. For me, the best potential campsites will start around 3000 ft, but in most instances, I end up camping around 4500–7500ft. I’ve only camped twice at higher elevations (Camp Muir at 10,000ft and Mount Adams at 12,ooo ft). Here in Washington State, if you look at temperatures on peaks North and South, West and East, you find that temperatures tend to be colder on the Eastside, as well as further North.

For planning purposes, I have formulated four typical scenarios:

1. Shoulder season averages: 25º to 45º F (September–November/March–June)
2. Winter averages: 25º F to 35º F (November–March)
3. Winter coldest averages: 10º to 25º F (September–June)
4. Winter deep cold averages (rare): –0º F to 10º F (occurring mostly December–May)

Notice, that 0º F weather is rare. It is so rare, I have never recorded it on any of my trips.

Based on this data, a 0º F (lower limit) sleeping bag will be sufficient for most trips throughout the Pacific Northwest winter season. A sleeping bag rated with a lower limit of zero degrees will likely have a comfort rating of around 15º F.

I don’t often use a thermometer, but the coldest thermometer temperature I have ever recorded is 6º F while camping on a frozen lake on the East side of the Cascade Mountains at about 5000 ft (March, end of winter). Because the expected temperature was going to be close to zero, I took a –20º F expedition sleeping bag, which allowed me to sleep comfortably with no concerns.

The Zero Degree Option

If you can only budget for one winter sleeping bag, get the 0º F option.

In the shoulder seasons (spring to early summer/late summer to fall) a 15º F sleeping bag will usually be sufficient. For rare deep cold winter nights, an “expedition” level (–15º or –20º F) sleeping bag will keep you comfortable. Most of the time, a 0º degree sleeping bag will be the most comfortable choice.

If you are fully committed to winter backpacking and only want to carry the minimum weight each trip requires, then you’ll want three sleeping bags, a 15º, a 0º, and an expedition-level bag ( –20º F or lower). With this range, you will be covered for almost every possible scenario, and never need to carry more weight than circumstances require.

Understandably, many people are not willing to budget for 3 sleeping bags. Another strategy is to add a sleeping bag liner to an existing shoulder-season sleeping bag.

If you are a cold sleeper, which is certainly the case for me, then I recommend the 10–15 degree rule. That is, always have a sleeping bag or sleeping system that is rated 10–15 degrees warmer than the expected forecast. If the forecast is 15º F, then a 0º (lower limit) sleeping bag is the best option. If you have a 0º bag, there are very few times when a trip will have an expected lower limit beyond your gear capabilities.

Or, if the forecast is 15º F, then a 15º (lower limit) sleeping bag with a liner that adds at least 10º would work.

Extra warmth is important to me because I sleep cold. I took my zero-degree Thermarest sleeping bag on a recent trip with a forecast of 15º F, my thermometer recorded 9º F just before sunrise, and I was comfortable. Temperatures don’t always match the forecast, so the 10–15º rule is a good safety measure.

In my view, if you have to do jumping jacks to get warm while snow camping, you have the wrong gear. Certainly, if you had an accident and couldn’t easily move, you need gear that keeps you warm while you are in place during the rescue.

Regardless of the sleeping bag you have, always check the mountain forecast carefully. Freakish lows are extremely unusual but they can occur. Back on 30 December 1968, Mazama and Winthrop recorded –48°F.

How Sleeping Bags are Rated

Down insulation is rated based on the number of cubic inches of loft one ounce of down produces. The loft is the primary way down captures and holds the warmth generated by your body. Down doesn’t generate warmth, it merely helps preserve the warmth your body generates. Most sleeping bags use 550–900 fill power ratings. 550 provides the lowest thermal performance and 900 the highest. But you must look at other factors too, such as how much down is used, how the bag is designed (baffle construction and draft tubes), and overall fabric quality.

0º F Down Sleeping Bag Examples

Zero-degree sleeping bags are the optimum bags for Pacific Northwest winters, so I will focus on some of the leading examples with that rating. The table below shows only 0ºF rated duck and goose down sleeping bags. Notice that the higher-rated down is lighter but more expensive. To simplify, all bags are the men’s or unisex version and in the regular size.

Some bags are available in long sizes and the Mountain Equipment Glacier 1000 model and the Sierra Designs bags are available in a women’s version. There are not many companies that offer zero and expedition-level sleeping bags tailored specifically for women.

Best Low-cost Down Sleeping Bag Options

The lowest-priced sleeping bags are synthetic. But if you are on a budget and want a low-cost down sleeping bag, the Sierra Designs Nitro (available in a women’s version) and the Therm-a-rest Oberon have good warm-to-weight ratios. Both are in the lower price range ($360–490), use 27–29 ounces of 800-power down, and ultra-light materials.

More expensive sleeping bags, such as those made by Western Mountaineering and Feathered Friends use higher fill power and put slightly more focus on durability rather than the most ultra-light materials.

A company called Hyke and Byke (not included in the table above) offers several zero-degree down sleeping bags in the $170–230 range. I know one backpacker who uses one of these and he seems content with it. Is the down responsibly sourced and it is a quality product? I don’t know. The actual down fill amounts are not posted and there is no independent rating or certifications.

Down vs Synthetic

The alternative to down is synthetic. Synthetic filling is less effective at capturing warmth than down. It is also bulkier, making it harder to pack, and it doesn’t retain loft for as long. Despite these disadvantages, synthetic sleeping bags have two important advantages:

• First, they provide more loft and warmth when they become wet from rain or tent condensation, and
• second, they are much more affordable.

The table below shows two synthetic 0º F sleeping bags compared with an equivalent down version. Notice the weight and price difference.

If you are on a limited budget or are unsure if winter backpacking is something you will enjoy, a synthetic 0º F bag might be a good option to consider. It’s how I got started!

Quite often in the Pacific Northwest, temperatures are slightly above freezing, making condensation a problem for down sleeping bags.

Even if it is 20–25º F, temperatures inside a tent may be above freezing. In such conditions, a 0º or 15º F synthetic sleeping bag could be more effective than a down bag on multiple night trips, especially in the shoulder season.

Packability

Synthetic sleeping bags are much bulkier than down bags when compressed. This photo provides a comparison. You may need a larger pack if you use a zero-degree synthetic sleeping bag, increasing your weight even further.

How Ratings are Determined

Some sleeping bag ratings are merely manufacturers’ claims. The first REI 0º sleeping bag I bought was shortly after reclassified as a 10º sleeping bag, before being discontinued. Nowadays, most major manufacturers have their sleeping bags rated independently using the European Norm (EN) 13537 and/or the International Organization for Standardization (ISO) 23537 testing methods. These protocols rate each bag for Comfort and Lower Limit. The Comfort rating refers to the lowest temperature the average “cold sleeper” will be comfortable, and the Lower Limit rating refers to the lowest temperature the average “warm sleeper” will be comfortable. This rating assumes the person is wearing an underwear base layer (top and bottom and a beanie) with a 1-inch thick insulating pad underneath the sleeping bag.

Some brands use the Comfort rating for women’s bags and the Lower rating for men’s and unisex bags when naming the bag. This means you cannot assume the lower limit rating is below the rating in the name. You must check the EN and ISO ratings instead. Also, be aware that some brands still don’t use the EN or ISO rating system. It is a useful system for comparing different brand models.

Ratings for Women vs Men

“Lower limit” and the “comfort” ratings mean different things for different people because everyone’s body and sleep comfort are not the same. It is generally assumed that men require less warmth than women, but clearly, some men require more. You must know your own requirements.

As mentioned above, some brands use the Comfort rating for women’s bags and the Lower rating for men’s and unisex bags. As an example, consider the REI “Zephyr 20 Sleeping Bag.” The women’s version is rated 22º F for comfort and the men’s version 21º F for the lower limit. Both are “Zephyr 20,” presumably meaning 20º F sleeping bags, but the men’s version has 15 ounces less insulation. Both cost the same and both are for 20º F, but the men’s version is lighter and less insulated. I would only consider the Zephyr for summer use, but I mention it here just to show an example of how a Women’s and Men’s sleeping bag compare.

Other manufacturers approach the issue differently. Mountain Equipment, for example, offers a model called the “Glacier 1000” in both women’s and men’s versions. Both have the same EN rating, but the men’s version has more rather than less insulation, and Mountain Equipment has its own “Good Night’s Sleep rating,” which is 7 degrees warmer than the men’s version, even though it contains only 2 oz more down. It is nice that Mountain Equipment has decided to create cold-weather sleeping bags for women, but before one makes much of this, note that when comparing the two bags together, there doesn’t appear to be any differences in the tailoring. Both the men’s and women’s versions have a shoulder girth of 62 inches and a hip girth of 54 inches. Color and the 2 oz difference in fill are the only things that distinguish the versions.

Sierra Designs are even more identical:

I have known men and women who say they use 0º F sleeping bags in 0º F weather and are comfortable. I’m not sure if they were accurately determining the temperatures they were experiencing, but I do know that this would not work for me. I never plan to use a sleeping bag in a situation where the lower limit matches the expected temperature. I always plan for 10–15º of extra warmth, without considering other factors such as hot water bottles, warmth captured by my tent, or additional insulated clothing.

One thing is certain, there is no consistent rule for distinguishing women’s and men’s sleeping bags. For example, the REI Co-op Zephyr 20 Sleeping Bag, there is 15 oz less down in the men’s version, but in the Mountain Equipment Glacier 1000 Sleeping Bag, there is 2 oz more. With the Sierra Designs Nitro, the specs are the same. This means it is not always the case that manufacturers make one gender more insulated than another, but rather that each manufacturer has its own approach.

When almost everything is the same, there is still somehow a slight difference in the final weight. This is likely because the women’s sleeping bag uses the same materials for a slightly shorter bag. My advice is to not concern yourself with gender labels and instead match your body and needs with the specifications that work best for you. For example, here are the three available sizes for the Sierra Designs Nitro. One of these is the women’s version.

Fits Up To: 5′ 8″ / 173 cm
Length: 74in / 188 cm
Shoulder Circumference: 58″ / 147 cm
Hip Circumference: 58″ / 147 cm
Footbox Circumference: 39″ / 99 cm

Fits Up To: 6′ 0″ / 183 cm
Length: 78in / 198 cm
Shoulder Circumference: 62″ / 157 cm
Hip Circumference: 56″ / 142 cm
Footbox Circumference: 40″ / 102 cm

Fits Up To: 6′ 6″ / 198 cm
Length: 84in / 213 cm
Shoulder Circumference: 64″ / 163 cm
Hip Circumference: 58″ / 147 cm
Footbox Circumference: 42″ / 107 cm

Does gender matter? Don’t women come in different sizes, just as there are short and tall men?! All the options use the same colors. Even if you are a woman who can fit perfectly in the woman’s option, you might want to choose the next size up for the extra space to put your boots at the bottom to keep them from freezing overnight.

Finding the Right Fit

If you can, visit a gear showroom and ask to try out the sleeping bag. REI allowed me to lay out a sleeping bag and get in so I could see how the width and length worked for me. At first, I disliked mummy bags, but with more experience I now prefer them. They are simply the most effective design for preserving body warmth and that’s the main purpose of a winter sleeping bag. That aside, you don’t want a bag that is too tight or the wrong length.

A bag that is tailored to fit your body length and shape will provide the most efficient warmth. However, having some extra space for gear such as a hot water bottle, electronics, clothing, and even boots can be beneficial. If my boots are wet from snowmelt, I bag them and put them inside the bottom of my sleeping bag on deep cold nights. This prevents the boots from freezing solid and being painful to put on the next day. If your boots are already frozen, don’t bother putting them in your sleeping bag. They will remain frozen and just keep your feet cold at night. Thaw the boots out instead with a hot water bottle in the morning.

The Total Sleeping System

Whatever sleeping bag you buy, it alone will not be enough. You have to have a complete system. For some hikers, their system will include a sleeping bag liner, extra quilt, or hot water bottle. Some strategies are optional, but the pad/mattress under the sleeping bag is essential, as is the need for wind protection. That is, you must have enough “R-value” or cold resistance under your sleeping bag.

For me, a total winter sleeping system consists of:

1. An appropriately rated sleeping bag
2. Two sleeping mats: One closed-cell pad and one air mattress with a combined R-value of at least 5. More is preferable (9 is achievable).
3. A tent for wind protection.
4. A complete dedicated head-to-toe base layer.
5. A hot water bottle (highly recommended, but optional).
6. Air-mattress repair patches.

Ideally, your air mattress alone should have a 5+ R-value. The closed-cell pad is primarily for protection, backup, and use around camp. In an emergency, someone can loan their closed-cell pad, and the two closed-cell pads combined will get the person with the failed air mattress through the night.

Protect Your Air Mattress from Sharp Objects

Quite often, your pack and other gear will be partially under your air mattress. The closed-cell pad can cover this gear and will help protect the air mattress from anything sharp. However, it is important to check the gear for anything that might puncture the air mattress such as unclipped pack straps, stoves, and stove windscreens. Some items can be wrapped in your gaiters to cover the edges.

Sleeping bag storage

Always store your sleeping bag in a hanging position or large breathable storage sack to help retain the bag’s loft. Never leave a bag compressed for long periods because this will damage the down or synthetic fibers.

When packing the sleeping bag in your backpack, only compress the sleeping bag as much as necessary. When you take it out to use it, fluff it up as much as possible. The effectiveness of the sleeping bag depends on its loft. Eventually, sleeping bags lose their loft and need to be replaced. Down sleeping bags last longer, maybe 10 years with weekend use, and synthetic sleeping bags last about half that amount of time.

Fun Facts

So what’s the warmest sleeping bag money will buy? Feathered Friends offers the Snowy Owl EX -60º F Sleeping Bag, for $1,139. This bag is described as “the warmest sleeping bag on the planet” and “the bag of choice for polar expeditions.” Thankfully, one doesn’t have to carry this 5 lb bag here in the Pacific Northwest.

What does a deep cold weather sleeping bag weigh if it is synthetic? Browning Camping makes a “McKinley” –30º synthetic sleeping bag that weighs 12 lbs 12 oz.

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