Build a Shelter
The most energy-efficient option is to create a nest. Pile up leaves, pine needles, and moss to create a giant sleeping bag that will trap your body heat. Make the mound about the length and width of a single mattress and five feet high, if possible. “You should have two feet of insulation below you and two feet above,” Nester says. “I’ve stayed warm like this on 10°F nights.” To tuck yourself in, scoop out a trough in the middle, sit inside butt first, then pull the debris over your body, working up from your feet.
On rainy nights fashion a lean-to against a short tree like a juniper. Use a sturdy, low branch as the shelter’s ridgepole. Knife-chop boughs (or scavenge) and lean them against the branch, then fill in the holes with forest debris so no light shows through. Insulate the floor with one foot of leaves and pine needles.
Also, site your shelter wisely. Avoid ravine bottoms, since cold air sinks, and high, wind-whipped spots. Instead, set up next to a broad
rock face or tree that has been soaking up the sun’s warmth
all day and will release it at night.
For hours of extra warmth, place football-size rocks at the campfire’s edge until they’re warm to the touch. Hug one against your chest (under a jacket but over a shirt), and put one between your legs and another near your neck or head.