Sleeping Outside in the Cold

Two Rules to Consider

Rule #1:  Plan for temperatures ten degrees lower than you expect to encounter--and make sure to take elevation into account. (Temps drop 3.5 degrees F for every 1000 feet of elevation you gain...)Obviously, your biggest challenge is going to be staying warm; as a corollary to that, staying dry (and, in particular, not sweating ) is another major objective.  You must stay dry—and that includes avoiding sweating.Rule #2: Clothing and sleeping bags don't create heat, they insulate. And unless you have some sort of heat source like a fire, you can create heat only two ways: 1) movement 2) eating.

• If you're going to be outdoors in freezing temps, plan to consume roughly 2 to 3 times your normal calorie count.
• The cold can depress a lot of your senses and motivations: Make sure your food sources are things you really WANT to eat, since you NEED to eat to stay warm.
• Remember that canister stoves don't work at low temperatures--so bring a white gas stove or plan to build a fire instead. (I would not count on a fire however, since dry wood is hard to find.) You'll need A LOT more fuel (gas or wood!) to boil and cook at low temps, so plan accordingly.
• If you can, invest in insulated bottles (which are good for year round use btw), and store all your bottles upside down (so that ice forms at the bottom, not the top)

Sleep System

As with clothing, the three layer system applies with your sleep system, but here your enemy is conduction (contact with ground) rather than convection (wind) or evaporation (water). You also need to protect the ground from your body heat (so the snow beneath you doesn't melt into a muddy puddle) as much as you protect yourself from the ground. From the ground up, your system should be:

1. Vapor Barrier. This is the Protective Layer of your system. Use thick plastic from the home center or an extra thick trash bag. Cut a shape a few inches larger than your body or sleeping bag..
2. Reflective Barrier.  An insulating layer. This bounces the heat back at you--and keeps your body heat from melting the snow/ice/ground underneath. You could use a mylar blanket, but I recommend using Reflectix insulation.  You can get a huge roll of the stuff at Home Depot and cut it to size.
3. Insulating Layer. An air mattress, unless it's a very fancy, high-R-value one like a  Therma-rest, will allow cold air to get underneath you and convect away body heat. Not good! Instead, use closed cell foam since it is an additional insulating layer. (How do you know foam is closed cell?  Try to blow air through it... if you can't, it's closed cell.)  Think cheap here: a yoga mat, packing material, or a cheap pad from a big box store.
4. Sleeping Bag. Your primary insulating layer. ring a bag that covers temps at least 10 degrees colder than you expect to encounter. You in your sleeping back represent another "three layer" system: 1) you are wearing a base layer  2) your bag has an insulating layer in the form of down or synthetic insulation, and  3) your bag has a protective layer of nylon to keep the down from spilling out.  If you're not in a tent or shelter, you'll need a further layer to protect your bag from the elements.
5. Still cold? Add a sleeping bag liner, or don additional, breathable, insulating layers of clothing--make SURE those layers are breathable; if you sleep in non-breathable layers, you'll wake up in the middle of the night, wet and cold.

Shelter

• If you are tenting, your sleeping system is your primary protection from the elements. Don't believe for a second that your tent provides insulation. While the tent can help prevent heat loss from convention (wind)—and it REALLY helps keep you dry—only really really really high end tents—that cost thousands of dollars—do anything to help insulate... and even those do very little.
• If you want to be warm, don't tent. Instead, build a snow shelter, debris hut, or quinzee.  These forms of shelter (look em up online) offer significant insulation and can be very very warm. Also, building such a shelter is a GREAT way to warm yourself up. Make sure you bring the necessary tools to build: generally that means a shovel and some pruning shears.

Other Tips for Cold Weather Camping/Sleeping:

• You MUST MUST MUST be wearing bone dry clothing when you go to sleep at night; if not, you'll be cold.
• Batteries lose power when cold.  Keep them on your body in your sleeping bag. You can bring other things in your sleeping bag to warm up...and eliminating airspace can help keep you warm... but don't pack the bag so much that you compress the insulation.
• Frostbite happens fast: consult online frostbite tables and make sure you have the right clothing to eliminate ALL EXPOSED SKIN if you need to.
• Your sleeping bag is not just for comfort: it's your last resort for safety and survival.  If all else fails, you should be able to climb in there and survive the cold, so don't skimp.
• Chemical hand warmers and foot warmers are wonderful things--and small enough that you can carry enough to cover your entire trip.
• You'll be wearing gloves or mittens, right? Remember too that you need to be able to prep food and do other work while wearing thick gloves. When assembling your gear list, keep that in mind!