The most challenging part of winter camping is the long cold night in your sleeping bag. If you stay ahead of the game, you can be pretty cozy. If you make any mistakes, you can be in for a miserable experience. Here’s a good trick. For centuries, Native Americans used rocks to cook and heat. Warmed on the fire, wrapped in cloth, and placed in your sleeping bag, a few rocks will provide many Btu’s of heat for hours. Just warming up your bag is over half the battle, so after your rocks cool you’ll be okay. Be careful, however. Rocks hot enough to boil water look no different than rocks cold enough to make ice. They can hold a tremendous amount of heat, and can easily burn right through cloth. Trust me. I know from experience! Don’t get them too hot. Another word of caution: you still need a sleeping bag or combination of bags warm enough for the conditions. Test your gear in the back yard before you go!