For those environments and conditions where you need the warmest sleeping bag you can get your hands on, there are some excellent choices out there. But there are also a number of things that add to the warmth of a sleeping bag, and will keep you warm and toasty. Obviously, the temperature rating of the sleeping bag is a good indicator of just how warm that sleeping bag will be. And there are always other things you can do, like wearing your sweater to bed, for instance, that will add warmth to a sleeping bag.
Warmest Sleeping BagWhat to look for when you're looking for the warmest sleeping bag.
- Draft Collar – You will likely want a draft collar, and a few other extras like a drawcord on the hood, to help add warmth. These features help to hold the warm air that your body generates inside the sleeping bag. If there are gaps in places, that warm air will escape, and cold air will have a chance to get inside your sleeping bag.
- Mummy Shape – Another thing that you definitely want when trying to get the warmest sleeping bag possible is a mummy shaped sleeping bag. The extra space inside a rectangular sleeping bag will only sap heat away from you and allow it to dissipate. Less space inside a mummy shaped sleeping bag means more concentrated body heat.
Warmest Sleeping Bag ReviewsReviews of some of the warmest sleeping bags, at a few different temperature points.
- Mont Bell U.L. Super Spiral Down Hugger #1 - With a temperature rating of 15 degrees, this option from Mont Bell makes an excellent four season sleeping bag. It uses 800+ fill down, but what makes it particularly warm is Mont Bell's unique construction method, where the baffles are cut at a 45 degree angle, so that the sleeping bag coils and squeezes around you at night as you move, increasing the warmth. It also has standard features like a draft collar, and the shell is water repellent, so you wont get cold if your sleeping bag gets wet. It weighs 2 pounds 4 ounces, or 1.02 kilograms.
- Mountain Hardwear Phantom - The Phantom is one of the better sleeping bags with a 0 degree temperature rating, and there are quite a few of them. It uses 800+ fill down, but the feature that makes it warmer than the competition is the relatively narrow alpine mummy cut. This cut eliminates as much unused space as possible inside the sleeping bag, without making things too cramped. So the heat that your body generates fills a smaller area, and thus makes you warmer. It also weighs an impressive 2 pounds 10 ounces, or 1.19 kilograms.
- Marmot CWM EQ - If you're serious about needing the warmest, then there are few sleeping bags that are warmer than the CWM, which has a minimum temperature rating of -40. This sleeping bag isn't messing around. The draft collar is top notch, and the drawcord around the hood provides a good seal without feeling uncomfortable. And the entire outer shell is waterproof, because when the temperature outside is -40, you really do not want the 800+ fill down inside getting wet and losing its ability to insulate. The bag weighs 4 pounds 10 ounces, or 2.o9 kilograms.