Cold braces, cold bites, cold is your enemy on long winter nights. When late-night temperatures plummet and warmth is precious for sleep, a good winter sleeping system cocoons you in comfy dreamland no matter what the conditions.

It's in the Bag
For winter camping adventures, you need a winter sleeping bag. Choose a model rated to -20 degrees Fahrenheit for anywhere, anytime, any conditions comfort, though a -10 bag suffices for most winter conditions you'll encounter in the Northeast. A zero-degree bag is adequate for many people in milder winter conditions (temps down to the teens); it also provides more versatility for shoulder season use when a true winter bag would be overkill.

Closely evaluate fit, a crucial element for winter warmth. First, zip up and check for length. Your feet should not compress the insulation in the toebox; a little extra length is nice for keeping boot liners and clothing warm at night. Second, test the hood. It should wrap comfortably and securely around your head, creating a good seal around your face to retain heat. Finally, make sure you can close and manipulate the internal neck baffle—an essential heat-trapping feature—even when fully zipped up.

Spend the extra money for down—it's worth it. Compared to its synthetic alternatives, a -20 degree down bag can weigh more than a pound less and pack radically smaller than its bloated cousin. Many winter bags feature a water-resistant shell, a nice feature for repelling the inevitable snow and frost that build up inside your tent. Sub-zero down bags start around $400 and rapidly go up from there; higher quality down (800 fill power and up) saves weight but adds to the price. Synthetic winter bags start around $250.

Nice Pad
Winter ground thieves body heat. Protect yourself from its freezing clutches with a sleeping pad. Pad warmth varies dramatically depending on thickness and type of insulating material; the more dead air it traps underneath you, the warmer it will be. This is indicated by the R-value—a measure of Resistance to heat transfer—a standard spec usually listed on the packaging.

You need more pad insulation in winter than in summer. A minimum R-value of 3.5 is usually required to fully insulate from snow-covered ground; R-values of 4 and above are recommended to ensure a toasty underside and account for cold spots caused by compression. (If your pad is too thin, heat bleeds through and melts the snow underneath—look for ice under your pad in the morning.) Stacking two pads increases warmth by roughly the sum of their respective R-values. A popular option is an inflatable and closed-cell foam pad stacked together for warmth and comfort (place the inflatable pad on the bottom).

A range of inflatable pads are available, though I recommend at least one closed-cell foam pad for any winter camping trip. They are lightweight, require no inconvenient inflation, immune to sharp winter tools (ice axes, crampons, etc), and durable enough to use outside and around camp.

Crank up the Heat
If you're looking for extra warmth, consider the following heat-boosting options. Wear extra layers inside your bag; make sure to have at least one layer over your head and neck. Add a sleeping bag liner inside your bag to increase warmth by up to 15 degrees. Use a chemical heat warmer or hot water bottle; place it inside your sleeping bag 30 minutes before bed for a toasty entrance. Maintain warmth on longer, multi-night winter trips with a vapor barrier liner, which prevents moisture (your nighttime perspiration) from entering—and compromising—your bag's insulation. Eat a candy bar or other high-calorie snack right before bed—or in the middle of a cold night—to fuel your body’s internal heat factory. And think warm thoughts!