Outside magazine, April 1995
Be overprepared. That's the Boy Scout hypermotto that many campers mistakenly live by when it comes to bedding down in the summertime. I for one used to take my fat, zero-degree sleeping bag on every warm-season trip. I certainly never froze, but I was always uncomfortable. It was either get inside the sleeping bag and wake drenched in sweat or sleep on top of it in my pile jacket and pants. I started to wonder why I brought the bag at all.
So I ultimately left it behind in favor of a summer sleeping bag. Summer bags are made specifically for kinder weather, and as a consequence they're lighter, more packable, and less expensive than their cold-weather relatives. And nowadays they're often designed for extra comfort: Summer's the time to appreciate that today's bags are being cut wider for more rolling room, have soft linings that feel good against bare skin, and incorporate zipper designs that maximize ventilation. Yet most can still be cinched down to ward off the chill of 3 A.M. A summer bag will keep you warm even if the temperature dips to freezing.
The first thing you should understand when shopping for a summer bag--or any sleeping bag--is that the touted temperature ratings shouldn't be taken as gospel. Those numbers are established by the manufacturers and may be useful for comparison, especially among different bags from one maker, but they're sometimes optimistic. As a rule of thumb, choose a bag rated five to ten degrees cooler than the lowest temperatures you expect to encounter. For most folks, such a bag will provide a sufficient reserve without being too hot; if you tend to "sleep cold," however, seek out a bag that's rated five degrees lower still.
Next you'll need to choose between down and synthetic insulations, and with summer bags that can be tough: Because they have a relatively small amount of insulation, most summer bags, synthetic or down, weigh around two pounds. All pack pretty well. And for $150-$200 you can find excellent candidates in both camps.
Other things being equal, down bags drape more comfortably and are more durable. After even a summer or two of frequent use, synthetic insulations can start breaking apart and losing their "loft," the quality that creates the dead-air space that insulates you. Down is much more resilient, and while almost any synthetic is superior to down when wet, few people should really care: In 24 years of camping and climbing in the rainy Pacific Northwest, I've never been the victim of a soggy bag. Unless you're a boater or sleep in a leaky tent, you shouldn't weigh the wetness factor too heavily.
Still, synthetic bags deserve respect and consideration. Their warmth-to-weight ratios can rival those of down bags, and synthetic bags in general are somewhat less expensive. The best synthetics available include Primaloft, Micro-Loft, Lite Loft, and Polarguard HV, as well as some proprietary spinoffs; each has its own virtues and shortcomings, but generally, if the bag you like is insulated with one of these materials, you can buy it confidently. If you decide on down, know that there's variety here, too. Down insulations are rated according to "fill power," the number of cubic inches an ounce of the stuff fills up. Down rated as "700-fill," for example, has more loft and thus greater insulating ability than 500-fill down--and, other things being equal, a bag made with it will be lighter and more expensive.
In shell materials, you're no longer stuck with ripstop nylon. New, soft but tough microfiber fabrics feel good against the skin and are so densely woven that they effectively block wind and moisture while remaining breathable. DryLoft, a version of Gore-Tex made specifically for sleeping bags and insulated clothing, is also an excellent choice, though its weatherproofness may be overkill in summer and it generally adds about $80 to the price. You'll also want to feel inside the bag to make sure it's lined with a material that you won't mind against your skin. Most summer linings are designed to wick away moisture or reflect heat back into the bag.
This brings us to bag shape. Mummy bags have the smallest volume and the tightest fit, making it easier for your body to warm the inside and harder for cold air to find its way in. But they're also more restrictive, and since these are summer bags, coldness isn't always a big concern. "Barrel bags," aka modified mummies, offer a bit more room, and semirectangular bags are even wider (and heavier). I've reviewed bags with a variety of silhouettes.
A few finer considerations: Does the zipper open from both top and bottom, to give you ventilation options? Is there a roomy footbox that lets you wiggle your toes? What about a good-fitting hood, which is necessary if you plan to bed down in chillier climes? If you want to snuggle with a partner, look for a bag that can be zipped to a mate (unless noted, all of the models here can).
Here's a selection of eight of the best summer bags, down or synthetic, that can be unstuffed and slid into.
Gold-Eck Husky 850
Expedition Trails Kodiak
Mountain Hardwear Crazy Legs Semi-Rectangular
and liner feel like satin underwear against your skin. Two zippers let you adjust ventilation, and the bag can be unzipped flat to form a quilt. But if you want to extend the Moraine's 20- to 30-degree rating, Marmot sells a matching hood ($51), or you can get the bag with a DryLoft shell ($90) if you often camp in wet conditions.
Western Mountaineering Badger
Douglas Gantenbein is a Bellevue, Washington-based freelancer who writes widely on the outdoors.