Nemo Sonic™: The best sleeping bag money can buy

Nemo Sonic™: The best sleeping bag money can buy

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This past April, as the first COVID lockdowns were being put in place, I took a road trip to Montana. I figured, if I’m supposed to isolate myself from others, I may as well go somewhere where not seeing any other people is a bonus. So off I went into the backcountry of the Big Snowy Mountains just outside Lewistown, Montana. It was beautiful. There was one problem though: Up at 7,000 feet, it was still fully winter. There was three to four feet of snow on the ground, and temperatures plunged into the single digits at night. I was prepared for the powder—I brought large snow shoes that kept me easily gliding on top—but the cold was another matter. I headed off into the wilderness with my REI Igneo 17 and I froze my butt off. I had to wear my heavy down jacket and pants inside the bag to find any semblance of comfort. That April night wasn’t the first time I had been a little cold while sleeping in a tent. But it was the coldest. And I had had enough. So before heading into the mountains of Colorado elk hunting last fall, I ponied up and bought what, in my opinion, is the best sleeping bag on the market: the Nemo Sonic.


The Nemo Sonic comes in two variants: a zero-degree bag and a minus 20-degree bag. As I’ve discussed before, temperature ratings for sleeping bags don’t necessarily mean comfort at that temperature, and since I live in Minnesota and enjoy winter camping, I decided to go with the minus 20-degree bag. And boy, was I glad I did. On our Colorado elk hunt, temperatures dropped to zero two of the nights. While my hunting partners nearly froze while wearing every article of clothing they brought inside of their 10-degree bags, I was comfy and cozy in only a set of long johns.

With a sleeping bag that keeps me comfortable in the coldest of temperatures, you might think I got a little too warm in more temperate weather. But the Sonic has a novel feature that is only found on Nemo sleeping bags: thermo gills. Thermo gills are two zippers on the top of the bag that, when “open,” create strips with little to no insulation, allowing heat to vent, but without creating a chilling, uncomfortable draft like opening the main zipper would do. By manipulating one or both of the thermo gills, I was plenty comfortable on nights where the temps stayed up in the 30s.

If you are looking for a single, do-it-all bag, the zero-degree bag would be the most versatile for most people. But if you already have a warmer bag and plan to do winter camping in the northern half of the continent, then the minus 20 bag will suit you better.


Not only is the Sonic warm, but it is unbelievably comfortable. Most sleeping bags will start to stick to bare skin after awhile, but the slightly thicker material on the Sonic doesn’t do this. Yet it’s still soft and comfortable. As an added bonus, this thicker material also makes the Sonic more durable and significantly reduces the down shedding that typically occurs with down sleeping bags.

Maybe the most important factor in overall sleeping bag comfort is fit. I’m a pretty big guy—6’2″ and 250 lbs. Most sleeping bags, even the long and wide versions, are more like a straitjacket than something to comfortably rest in. I purchased the long version of this bag, so I knew the length would be OK, but I was concerned because there was no wide option. As it turned out, there was plenty of room for me. As a side-sleeper, I was even able to turn from side to side comfortably.

It’s the little things

The material on the outside of the bag improves your comfort in the wilderness, too. Frost and condensation buildup on your tent transferring to your sleeping bag can make even the warmest bag chilly by the time you wake up. A lot of sleeping bags combat this by making the toe box waterproof, but you can still wake up in a damp bag. But the entire exterior of the Sonic is waterproof. Now, I’m not saying it will stand up to actual rain while cowboy camping, but frost and condensation inside of your tent will not cause any problems.

There are a couple of minor details where Nemo went above and beyond, which really made a surprising difference in overall comfort. While every even remotely serious backcountry sleeping bag has a flap covering the zipper to prevent a draft through the zipper, the Sonic has two draft tubes, both above and below the zipper, to completely eliminate any draft through the zipper. Likewise for the draft collar: Every bag has one along the top, but the Sonic has one both along the top and one along the bottom under your neck, which connects by hook-and-loop fastener and can then be cinched down with a drawcord to completely isolate your head from your body, keeping all cold air and—especially important for a side-sleeper like me—the moisture from your breath out of the main body of the bag.

Finally, there is a small pocket to keep your phone or other electronic device in, preventing the cold from draining the battery.

The downside

If it seems like I’m in love with this bag, I am. But I do still have a couple beefs: two small ones that are really just minor inconveniences, and one serious one. First, the phone pocket isn’t very well designed. It’s a nice feature, but the zipper is small and difficult to locate while inside the bag, and the pocket is a little small; a phone on the bigger side may not fit. Second, the zipper gets stuck on the draft tubes constantly. However, the material is durable enough that there’s no worry it’s going to tear and thick enough that it doesn’t actually get stuck in the zipper. It’s just an annoying snag that takes a little jiggering.

My main beef, however, is the cost. While I say that the Nemo Sonic is the best bag on the market, at $600 for the -20 Long model, it sure is priced like it. Even the “more affordable” zero-degree bag in regular length is $500. To me, this is a borderline extortionate price. But if you’re patient, Nemo does occasionally have sales where you might be able to get a 20-30 percent discount. With an item priced this high, that leads to some pretty serious savings, but such sales are rare—once or twice a year. But if money is no object to you, or if you are about to embark upon a serious cold-weather expedition where deep cold and/or bad weather is a real possibility, it’s absolutely worth the money.

Images courtesy of manufacturer.

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