In Tents Cold 

As winter approaches, grizzly bears become hyperphagic: That is, during this annual autumnal phase, bears aggressively consume as much food as possible, packing on essential body fat they will need to survive until spring. Even with all this preparation, bears' basic bodily functions slow as they enter hibernation, allowing them to conserve energy through long winters in their dens. Their respiration and heart rate slow. Metabolism slows. Body temperature lowers. If you've ever experienced winter camping, you might have some idea what hibernation feels like—gorging on calories, and then burrowing into a warm den for a long dark night of fitful sleep.

Winter camping is for hearty souls. Though it may seem an elite activity achievable only by the likes of Caroline Gleich and Conrad Anker—professional mountaineers decked out with top-of-the-line gear—it's certainly possible for anyone with the desire, some gumption and a little know-how.

My earliest experience with winter camping is less an example of preparation and good practices than a story of learning through trial and error. It goes back to a cold September in Wyoming—winter comes early in those parts. I was on a work assignment camped out in the Gros Ventre Wilderness. Night temperatures were consistently dropping into the low 30s. I'd been pitching a tent to sleep in, but no matter what I tried, I couldn't get warm.

One night, I decided not to set my tent. Instead I spread my space blanket—a 7-by-5-foot sheet of aluminum lined with a plastic polyethylene film and Astrolar reinforcing fabric—out on the ground. My sleeping pad and bag went on top, and after sliding into my bag I pulled the other half of the thin blanket over the top and, in true burrito fashion, tucked the end back under the other side of my pad. In the morning, a thick layer of ice crystals spread over the top of the space blanket, but I was warm, dry and rested. Without knowing it, I had employed some of winter camping's best practices

People often think that it's the clothing material, or sleeping bag, that keeps them safe from the cold. In reality, what insulates your body from winter chill is air. Between your skin and each layer of clothing, or between the feathers in a down sleeping bag, is a micro gap of space—what's called "dead air." This dead air is a poor conductor of heat, and holds the warmth we generate close to our body. When we layer clothing or sleeping materials, each added layer creates another air gap, increasing heat retention.

Back in Wyoming, it took a lot longer for my body to heat the space of the tent than to heat the spaces between my bag and my space blanket. It also helped that my space blanket, a recommended addition to any wilderness first-aid kit, was designed specifically to radiate my body heat—as much as 80 percent—back at me.

I haven't always been so lucky. There have been plenty of failed winter camping trips, including one that, in my circle of friends, will go down in infamy. We'd stopped for a night just outside of Kanab and pitched an enormous family-size canvas tent atop 6 inches of old snow. By morning my feet were so white and numb, I worried I wouldn't be able to revive them. My friends didn't fare much better.

There were a number of things we'd done wrong, including trying to winter-camp in a three-seasons tent; only four-season tents are designed for the cold. But the experience could have been entirely different, even with our summer gear, if we'd followed some essential winter camping protocol: warm up before you go to bed (do jumping jacks if you have to); brush off snow from your clothing and shoes before getting in the tent (to avoid condensation inside); take off damp clothes (like socks) and replace them with dry layers; wear layers to bed; get a bag that's rated lower than the nighttime temperature you will be in (if it gets to -15 degrees F, bring a bag rated for -30 degrees F) or use a bivy sack inside your bag (it can increase the rating by 10-15 degrees).

Winter doesn't have to mean packing your camping supplies into storage until spring. It just means planning for different conditions, and gathering around a blazing campfire under the stars before slipping into a warm den for a long, long sleep. CW