Nemo Sonic -20 Degree Sleeping Bag Review
A few years ago I was on a backcountry trip at 9200' and we had a few unexpectedly cold nights, as low as minus 8 Fahrenheit. I spent these nights wearing multiple base layers, a coat, 2 pair thick wool socks, a balaclava shivering in my lightweight 15 degree bag. I needed a much warmer bag for these situations.
After a little research I decided on the Sonic -20 from Nemo. It cost as much as two high quality 20 degree bags so I had a hard time hitting the "Buy It Now" button until I remembered freezing (see photo on left!) in my 15 degree bag. That made it easier, but not easy. Then I realized there was an availability problem. After almost 2 months one became available at the local REI, the local REI in Anchorage, AK and I live in North Carolina! Fortunately REI shipped it to my local store at no charge and I was in business.
This bag was pretty expensive and I've come to believe it was worth the price of entry, but I don't get as much use from it as I do my 15 degree bag and 30 degree quilt. It is very versatile. The first thing I noticed is that this bag is large, roomy and heavy. If you like to toss and turn, like me, this is a great bag. The waterproof footbox is breathable and huge. On the colder nights I've used this bag I put extra base layers and sox in the footbox so they are warm in the morning and I suspect if it were below zero they would help take up some of the dead space to help warm your feet. The bag also has some stretch at the area the knees occupy so it is easy to sit up in this bag and even to cross your legs. The hood is the best I've tried with room inside for a small pillow when left open or it can close down with the excellent drawstring to only allow a tiny space for air to enter/exit and the draft collar has a little bit of velcro on the end so you can secure it on really cold nights. If it's not so cold, I've slept in 30 degree weather with this bag, there are two zippered "Thermogills" to allow excess heat to escape. In the low 30's I had both gills open and slept very comfortably in shorts and a long sleeve synthetic tee shirt. There is a small zippered pocket just outside the draft collar for electronics, batteries, etc but I have not used it. I prefer to keep those small items inside the bag in cold weather. The exterior of the bag seems very tough and it has seen some pretty hard use over the last three years with no visible scuffs or tears. It comes with a very large mesh storage bag to maintain loft and s stuff sack as well.
What's not to love? Well to begin with it's heavy, in the stuff sack it is close to 4 pounds. That's more than twice the weight of my REI Magma 15 and at my age on the side of a mountain with a heavy hunting pack with 4 or 5 days of food and gear that makes a real difference. It also doesn't pack down very small. Compared to my Magma 15 and Hammock Gear 30 degree quilt this thing is huge, larger than both of those combined. In 2022 I went on a solo elk hunt in the Weminuche Wilderness and found that the volume of this bag really limited the gear I could carry in my 3200 CI pack unless I attached it to the outside of my pack and the sleeping bag is the last item I want outside my bag. The zipper can be a little finicky but is useable. And all the room I mentioned also creates dead space inside leading to longer warm up times when I get into the bag.
Overall I am very happy with the bag. Nemo says this is the only bag you need from -20 to 40 degrees. I've not yet had the opportunity to test it in -20 weather, but I've slept in 9 degrees with a single base layer and was toasty! This is a well made, comfortable, feature filled expedition bag capable of keeping you safe well under zero degrees Fahrenheit. I highly recommend it.