Perhaps you’re thinking about getting into some winter camping. Maybe you’re looking to venture out later in the fall—or earlier in the spring—and happen to be a cold sleeper. The question will eventually arise: What do I need, a 3-season sleeping bag or a winter sleeping bag?
At face value, the answer seems easy: if it’s winter, you take a winter sleeping bag. In reality however, it’s not so clear cut. For starters, winter has big regional variances. Winter in the Mojave Desert is going to be different than winter in British Columbia. In fact, winter in eastern BC is considerably different than winter on its western coast.
Secondly, everybody is a unique sleeper. Some of us sleep particularly cold or warm. Some of us like to lay peacefully on our backs all night, while others like to curl up on our sides. The point is, good sleep in the backcountry is about building a complete sleep system that suits your unique needs.
So let’s take a look at what you need to know regarding 3-season sleeping bags vs. winter sleeping bags.
3-Season Sleeping Bags
3-season sleeping bags are intended for use in spring, summer and fall. Because of the temperature variance that can occur over those three seasons, the 20F/-6C is a very popular temperature rating for a 3-season sleeping bag. However, a bag rated 32F/0C is ideal for most people in sub-alpine environments and can save some weight. Versatile by design, a 3-season bag balances warmth and comfort with being light and compact so you can take advantage of it during all three of those seasons.
Here is our line-up of 3-Season Sleeping Bags:
- Parsec™ 20F/-6C
- Hyperion™ 20F/-6C & Hyperion™ 32F/0C
- Ohm™ 32F/0C
- Questar™ 20F/-6C & Questar™ 32F/0C
- Saros™ 20F/-6C & Saros™ 32F/0C
Winter Sleeping Bags
Winter sleeping bags are designed to keep you warm and comfy in sub-freezing temperatures. Heavier than 3-season bags, the extra bulk is absolutely worth it when the thermometer drops. The 0F/-18C rating is a kind of benchmark temperature rating for a winter sleeping bag. However, we all know that winter doesn’t stop getting cold when the thermometer hits zero. Winter bags also come in sub-zero temperature ratings, like the Polar Ranger, for the coldest places on earth.
Here is our line of winter sleeping bags:
Understanding Temperature Ratings
The most obvious difference between a 3-season sleeping bag and a winter bag is the temperature rating. Sleeping bags are rated according to the EN/ISO Standards. The EN 13537 Standard was introduced in 2005 and the ISO Standard came along in 2017. Understanding these ratings allows consumers to make direct comparisons of standardized sleeping bag temperature ratings across models and brands.
You’ll notice that most of our winter sleeping bags have a temperature rating of 0F/-18C, and the 3-season bags have a rating of 32F/0C or 15F/-6C. These specific ratings represent the lower limit of the ‘Transition Range‘. According to the standard, at that limit, a typical sleeper, using just the rated sleeping bag for warmth (plus base layers), is “in a situation of fighting against cold (posture is curled up inside the sleeping bag), but in thermal equilibrium” and not shivering. It can be understood as the performance limit of your bag. From that point up to the comfort range is the realistic range in which you’ll likely be comfortable in a given bag. Below it is the ‘Risk Range’ where an average person will likely begin losing heat, unless more insulation–like an additional sleeping pad, quilt or more clothing–is added. While most manufacturers need to send their bags out for testing, we have an on-site cold chamber so we can test our designs throughout the development process, assuring they meet our design goals.
We present these ranges—in addition to the numeric rating—to account for the individual differences between sleepers. With a range, our customers can make a more informed decision on which bag is right for them. If you’re a warm sleeper, perhaps you can comfortably use a 3-season sleeping bag for late fall adventures when the weather is threatening winter conditions. If you’re a cold sleeper, you may want to consider bumping up to a winter sleeping bag for added warmth in the same situation.
Key Feature Differences
Why would you carry a 3-season sleeping bag if you might encounter wintry weather? Why not err on the side of caution and ensure you are warm with a winter bag? The most significant determining factors are the differences in weight and packability.
Weight & Packability
To provide all that extra warmth, winter bags generally weigh more and don’t pack as small as a three-season bag. For example, our Questar™ 20F/-6C weighs 2 lbs 3 oz (990 g) and the winter-ready 0F/-18C model weighs 2 lbs 11 oz (1,210 g). In addition to the added weight, a winter bag takes up more space–packed and unpacked. However, if you need the warmth, these are compromises worth taking.
Insulation & Warmth
What accounts for the difference in weight and packability between a 3-season sleeping bag and a winter bag? The primary factor is the amount of insulation in the bag. Simply put, more insulation means more warmth.
However, the type of insulation has an impact on both of these properties. Each model in the Questar and Saros lines are essentially the same from a bells and whistles perspective, but the Questar bags are filled with 650-fill Hydrophobic Down, and the Saros bags are filled with our proprietary eraLoft™ synthetic insulation. You can find a deeper discussion of the performance benefits of each insulation type here, but the bottom line is that between two bags of the same temperature rating and construction, the down bag will weigh less and pack smaller.
What About Quilts?
All of our quilts are considered 3-season quilts. The open-bottom design of a quilt limits its ability to achieve the heat retention required for winter camping. However, quilts can be an incredibly valuable piece of winter gear when used as a layer.
Those of us involved in year-round pursuits that need both 3-season and winter warmth may opt to simply have multiple sleeping bags. However, there is a slightly different way that offers more flexibility. Adding a quilt (or blanket) on top of your sleeping bag works the same as layering your clothes. By adding a quilt or blanket, you add warmth and boost the overall temperature rating of your sleep system.
Example: if you’re using a Parsec 20F/-6C 3-season sleeping bag, and you layer a Corus™ 32F/0C quilt on top, your new overall temperature rating would be about 5F/-15C. This is suitable for many winter pursuits. Moreover, in the summer, when the weather is warm enough, you can leave behind the Parsec 20F/-6C and use just the lighter-weight Corus 32F/0C, for greater overall efficiency. You can even try two quilts for shoulder season, saving the sleeping bag for the coldest days of the year.
The quilt is an incredibly versatile piece of gear that allows you to create an adaptable sleep system. Finer control of your system’s temperature rating allows you to dial it in right to your comfort preferences.
Also, keep in mind that your sleep system’s warmth is the sum of its parts. No sleeping bag will keep you warm and comfy without the proper sleeping pad beneath it. You can further dial-up your system’s overall warmth by using a mattress with a higher R-value or layering something like the ultralight Z Lite SOL under your existing mattress. Doing so will add warmth and durability to any sleep system. And just like adding a quilt on top of your sleeping bag, the extra layer can often bump your three-season system into the shoulder seasons, if not fully into winter, with greater versatility for every season.
There’s much to know about finding the right sleeping bag for your needs, but we hope this piece helped add some clarity to your search. If not, or if you have any questions, don’t hesitate to leave us a comment or reach out!
- The Ultimate Guide to Sleeping Bags & Quilts
- How to Build a Fall Sleep System
- How To Build Your Winter Sleep System
Updated. Originally Published October 19, 2021.