Best Arctic Sleeping Bags for -20°F to -40°F in 2026

Buy the bag whose lower limit covers your coldest night, not the one with the biggest number in its name. For tent nights at -30°C (-22°F) and colder, the Marmot CWM -40 is the -40°F down bag most shops carry; the Western Mountaineering Bison GWS is the warmer, dearer expedition choice. If you are sleeping in a cabin, a car or a heated base camp, a synthetic 0°F bag such as the TETON Sports Celsius XXL costs a fraction as much, and the TETON Mammoth is the same idea for two.

We have not slept in these bags ourselves. Every rating, weight and price below is the maker's or a named retailer's or tester's, with the source beside it, read in November 2026.

Sleeping bags carry up to three temperatures, and the one in the name is usually the coldest of them. Under the ISO 23537 and older EN 13537 tests, comfort is the temperature at which an average cold sleeper is comfortable, the lower limit is where an average warm sleeper still sleeps curled up, and extreme is survival only (REI's explanation of the ratings).

How far apart they sit is the surprise. A retailer listing for the Mountain Hardwear Phantom -40 gives an ISO comfort rating of 13°F and a lower limit of 0°F for a bag sold as "-40" (Steep and Cheap). TETON Sports, for its own 0°F bags, tells buyers to add 20 to 30 degrees to find the comfort temperature. Rab publishes only a limit for the Expedition 1000: -30°C (-22°F), with comfort marked "N/A".

So for a trip: find the coldest night you expect (our how cold it gets on aurora nights has the averages for Tromsø, Lapland, Iceland and Fairbanks), then choose a bag whose comfort or limit rating is at or below it, and treat the name as the extreme.

The Bison GWS is Western Mountaineering's expedition bag, rated to -40°F (-40°C) with 42 oz of 850+ fill goose down under a Gore Windstopper shell. The maker lists it at 2,095 g in the 6 ft length and $1,400 to $1,440, and sells extra down ("overfill") that adds about 5°F; overfilled and custom bags cannot be returned.

It is the one to buy if you will spend many nights in a tent in interior Alaska, the Yukon or Finnmark in January and want the margin. Western Mountaineering sells through outdoor dealers rather than Amazon, so start at the maker's page, which lists stockists.

The Marmot CWM (the name stands for Cwm, the valley under Everest) is rated to -40°F / -40°C, filled with 800-fill goose down and shelled in waterproof Pertex Shield, which matters when frost from your own breath builds up inside a tent. Trailspace lists the regular at about 2,066 g and the MSRP at $819, with retailers between roughly $697 and $949.

It is a little heavier and a little cheaper than the Bison, and it is the -40 bag most likely to be in stock somewhere this winter.

Check Marmot CWM -40 price on Amazon

Rab's Expedition 1000 carries 1,000 g of 850-fill down and is rated by its limit, -30°C (-22°F) under EN 13537; Rab marks the comfort rating "N/A". Retailers list it at around 1.6 kg. For colder trips the same family has the Expedition 1400, which retailers list at -40°C and about 2.1 kg.

Pick the 1000 for spring trips, coastal Norway and Iceland, or for a sleeper who runs warm; the 1400 if your coldest night is inland in midwinter.

Check Rab Expedition 1000 price on Amazon

The NEMO Sonic -20 has an ISO lower limit of -20°F (REI's listing) and about 2.3 lb of 800-fill down in the regular size (OutdoorGearLab). Its "thermo gills", zippered vents along the top, let you dump heat on a milder night without opening the main zip.

It suits most aurora-season camping in Iceland, coastal Norway and Swedish Lapland, where nights between -10°C and -25°C are typical, and it is a lot of bag for less than an expedition -40.

Check NEMO Sonic -20 price on Amazon

Many people searching for an "arctic sleeping bag" need one for an unheated cabin, a car on an aurora chase, an ice-fishing shack or a hunting camp, not a tent at -40. For that, a big synthetic bag at a fraction of the price does the job:

• TETON Sports Celsius XXL 0°F: a roomy rectangular-ish bag, about 6.5 lb by the maker's figure. TETON itself says to add 20 to 30 degrees to the 0°F rating to find comfort, so think of it as a bag for nights around -5°C to -10°C (20°F to 10°F).
• Coleman North Rim 0°F: a synthetic mummy that fits sleepers up to 6 ft 2 in (Coleman); listings put it at about 6.5 to 7 lb. Owners on Trailspace call it warm and cheap but heavy.

Neither belongs in a tent at -30°C. Doubled up (one bag inside the other) or over a fleece liner and a warm pad, they stretch further.

For couples, the TETON Mammoth is a queen-size double sleeping bag rated 0°F by TETON, weighing 15.1 lb: one for a cabin, a truck bed or a heated tent at base camp, not for carrying. Check the listing before you buy: TETON also sells a 20°F version of the Mammoth, and some shops mix the two up.

Check TETON Mammoth 0°F double price on Amazon

The bag is only part of the system. Most heat on a cold night goes into the ground, so lie on a winter-rated pad (the higher its R-value, the less heat the snow takes), or a foam pad under an inflatable one. Change into dry base layers before you get in, and keep tomorrow's clothes and boot liners in the bag with you. Eat something fatty before bed, and pee before you settle: your body stops spending heat on it.

A liner adds a few degrees and keeps the down clean, and a hot water bottle in a sock at your feet is the oldest trick there is. If you are sleeping out in serious cold, know the signs of frostbite and hypothermia, and how to make an emergency snow shelter if things go wrong.

Check winter sleeping pad price on Amazon

• Western Mountaineering, Bison GWS product page (rating, fill, weight, price, overfill).
• Trailspace, Marmot CWM -40 (weight, MSRP, retail range); Backcountry listing (price).
• Rab, Expedition 1000 product page (EN 13537 limit, fill); retailer listings for weights and the Expedition 1400.
• Steep and Cheap, Mountain Hardwear Phantom -40 listing (ISO comfort and lower limit, fill).
• REI, NEMO Sonic -20 listing and REI's guide to temperature ratings; OutdoorGearLab, NEMO Sonic -20 review (fill).
• TETON Sports product pages (Celsius XXL and Mammoth ratings and weights, comfort advice); Coleman, North Rim page; Trailspace owner reviews.

Read in November 2026. Prices move; the Amazon links show today's. North Wiki earns a commission on purchases made through them, at no cost to you.