How To Stretch Your Sleeping Bag’s Temperature Rating

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What steps can I take to make a 28°F sleeping bag stretch into colder temps than it is designed for? Looking like low 20s is a possibility! —Josh, San Diego, CA

Without good sleep, it’s impossible have a good hike—and without staying warm enough, it’s impossible to get good sleep. Unfortunately, building up a quiver of sleeping bags is expensive, and not everyone is wild about the idea of running out to grab a new one just because it’s going to be a little colder than usual.

Luckily, there are lots of tricks you can put up your sleeve to make a bag warmer. Here are a few of my favorites. Note that these will win you a few extra degrees, but probably won’t be enough to push into an entirely new season. For another, relatively low-cost option, try calling your local retailers to see if they rent sleeping bags.

Make sure to use a warm pad to prevent cold seeping up from the ground. If you use an air pad, look for one with insulation, like the Big Agnes Q-Core SLX. Another option: Layer a closed-cell foam pad over your existing pad for an extra layer of warmth.

Add a liner to make your bags 10 degrees warmer or more. The Sea to Summit Reactor Liner helps make bags a little toastier with its 14-degree rating, weighs about as much as 2 sticks of butter, and retails for less than $70.

Cuddle with a hot water bottle. This is my favorite trick; I rarely go to bed without one in fall through spring trips. Just boil some water before bed, make sure your bottle is totally leakproof (liter-size Nalgene’s are perfect), and snuggle up, moving it around to warm various body parts throughout the night.

Don’t overdress. If you wear too many bulky layers to bed, your bag’s insulation can compress, and then it can’t do its job. Wear just enough to take up all the extra space in your bag (long johns and a light puffy jacket or vest usually do me just right).

Wear a hat and cinch up the hood. Make use of those drawcords around your face to make a nice tight seal and create a breathing blowhole. Just make sure not to breathe inside your bag, as that moisture can wet the liner fabric or even freeze if it gets cold enough.

Eat a good dinner and have a snack before bed so your inner furnace is cranking throughout the night.