Review: Sierra Designs Cloud 35 Sleeping Bag

Ultralight Sleeping Bag
Sierra Designs Cloud 35
$300, 1 lb. 7 oz. (men’s regular)
Sizes: men’s regular and long (35- and 20-degree), women’s 20-degree (one size)

Mummy-style sleeping bags deliver high warmth efficiency for their weight because they trap heat so well—but can sometimes feel like they’re trapping you inside, too. Backpacking quilts mimic the feeling of sleeping under a comforter at home, but may too easily let cold air underneath on chilly nights outdoors. With its zipperless design and integrated comforter in the bag’s upper half, the Sierra Designs Cloud 35 bag achieves the strengths of mummies and quilts without their weaknesses.

I slept in the ultralight men’s Cloud 35-degree for eight nights on a backpacking trip of over 120 miles through the High Sierra in August, mostly on the John Muir Trail, with lows often in the 40s Fahrenheit and strong wind; for four nights that ranged from the high 40s to near 60° F on a 78-mile backpacking trip on the Wonderland Trail around Mount Rainier in early September; and on five nights of camping in Idaho’s City of Rocks National Reserve in June and early October, with lows down to the 40s—staying quite warm wrapped inside the bag in temps not far above its EN comfort rating of 36° F/2° C. The 35-degree bag has an EN limit rating of 26° F/-3° C.

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The Sierra Designs Cloud 800 35-Degree sleeping bag.
The Sierra Designs Cloud 800 35-Degree sleeping bag with comforter flap open.

Weighing just under 1.5 pounds, the Cloud 35 has a good warmth-to-weight ratio, thanks to being stuffed with 9.5 ounces of PFC-free, 800-fill, water-resistant Dridown down (in the regular, 10.4 ounces in the men’s long, and 20.5 ounces in the women’s 20-degree version). That high-quality down also makes the 35-degree bag very packable, stuffing to a compact 13×7 inches.

Most unique about the Cloud bags is their zipperless, comforter-style design with a crescent-shaped flap on the upper half of the bag that you can flip to one side or wrap around your torso like a blanket. The comforter flap’s crescent shape maintains some tension on the flap to keep it from opening up while you sleep, and an insulated shoulder pocket at the flap’s upper corner helps keep it wrapped around you.

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The Sierra Designs Cloud 800 35-Degree sleeping bag.
The Sierra Designs Cloud 800 35-Degree sleeping bag with comforter flap closed.

The design’s benefits include much easier ventilation and exiting the bag—no fumbling with a zipper in the middle of the night—and a sleeping experience more like lying in your bed than squeezed inside a zipped-up mummy bag. The single flap also reduces bag weight compared to having two overlapping flaps.

The Sierra Designs Cloud 800 35-Degree sleeping bag foot box.
The Sierra Designs Cloud 800 35-Degree sleeping bag foot box.

While not as secure as a zipper, the flap mostly stayed wrapped around me unless I turned a lot. As a side sleeper, I found the flap, not surprisingly, stayed in place over me better when I slept on the side where the flap opens, with a hand in the shoulder pocket to hold the flap in place, than when I slept on my opposite side, where the flap and shoulder pocket could slip off my elevated shoulder. On a night that I slept under the stars and the wind blew hard most of the night, it did continually blow the flap off me unless I slept on the same side, with my hand securing the flap closed.

The Cloud 35’s dimensions of 60 inches at the shoulders, 58 inches at the hips, and 40 inches at the feet (men’s regular) offer unusually spacious dimensions for moving around—again, replicating a sleeping experience closer to your bed at home than a mummy bag.

The adjustable hood snugged fairly well around my head on cooler nights. You can insert a 20-inch-wide air mattress into the half-length fitted sleeve on the bag’s bottom side to keep from sliding off the mat—although that prevents side sleepers from turning the bag (and its hood) with their body. The 15-denier shell fabric has enough durability for normal use, but avoid catching this lightweight fabric on sharp edges.

The Sierra Designs Cloud 20 ($320, 1 lb. 15 oz.) comes in both men’s and women’s versions; the women’s bag comes in one size with a length of 74 inches and differs from the men’s primarily in the amount and placement of the down fill.

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Sierra Designs Cloud 35

The Verdict

Stuffed with high-quality, 800-fill, water-resistant Dridown, the zipperless Sierra Designs Cloud 35 and Cloud 20 bags carve out a unique niche among sleeping bags for backpacking with exceptional comfort along with good warmth and packability for their weight.


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See all of my reviews of sleeping bags that I like and all of my reviews of backpacking gear, and my articles “Pro Tips for Buying Sleeping Bags” and “10 Pro Tips: Staying Warm in a Sleeping Bag.”

Whether you’re a beginner or seasoned backpacker, you’ll learn new tricks for making all of your trips go better in my “12 Expert Tips for Planning a Wilderness Backpacking Trip,” “10 Tricks for Making Hiking and Backpacking Easier,” and “A Practical Guide to Lightweight and Ultralight Backpacking.” With a paid subscription to The Big Outside, you can read all of those three stories for free; if you don’t have a subscription, you can download the e-guide versions of “12 Expert Tips for Planning a Wilderness Backpacking Trip,” the 10 tricks for making hiking and backpacking easier, and the lightweight backpacking guide without having a paid membership.

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NOTE: I tested gear for Backpacker Magazine for 20 years. At The Big Outside, I review only what I consider the best outdoor gear and apparel. See my Gear Reviews page at The Big Outside for categorized menus of all of my reviews and my expert buying tips.

—Michael Lanza

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