Agree with all the comments. Sleeping in the cold can be an enjoyable experience if you are prepared.

Typically for us, it starts with a good tent and fly. Unless the weather is really foul, the fly is kept loose especially at the top of the tent as there are air vents that help disperse condensation out.

For cold sleeping, I use; Therm-a-Rest RidgeRest SOlite sleeping pad, -10 rated synthetic sleeping bag, bag liner, synthetic medium weight long johns, undershirt, polar fleece pullover. 2 layers socks and a hat if needed.

Misc tips:

- Instead of doubling sleeping bags (unless they are warm rated types) consider using a liner. These are generally cheaper, much less bulky to carry and can add 5-10F of added warmth. The other positive is they much easier to clean then a sleeping bag as most can be washed in a household washing machine and either dried on low heat or hung to dry.

- Some people find a neck warmer helps keep a draft of the neck. A balaclava goes further by keeping the neck, face and head covered.

- Don't sleep with the sleeping bag over your head. All the moisture you exhale is going directly into the bag. If you want to keep your head and face warm, see above point.

- Don't sleep with just an air mattress under you as the cold is conducted right from the ground and up through the air mattress. Use a good quality closed cell sleeping pad such as the Ridgerest mentioned on top the air mattress.

- Before bed, fill your water bottle with hot water (or tea hot chocolate etc) for overnight warm drinks) and keep in the sleeping bag. Make sure the bottle is covered so that it does not burn you. A spare sock or extra shirt works great for this purpose. Chemical heat packs are another option instead of the water bottle.

- Eat bedtime snacks that have some fat and calorie content to keep your body warmer. You cannot beat Peanut butter sandwiches for this. I personally prefer some pepperoni sticks as they usually have a good fat content. Some old time explorers and modern day Expeditioneers carry and cook up bacon for their bedtime snacks in extreme cold conditions. Others carry and eat various nuts and trail mixes.

- If your camping area is subject to wind, try and setup the tent out of wind. If not possible, position the tent so that a window or the door is into the wind and open very slightly. Be doing this, the tent is pressurized so to speak and will stop that annoying flapping of the tent when the wind blows for hours.

- If you hang a plastic, woven or sil type tarp above your tent, weight it down with a piece of wood or something of similar weight. This helps to keep the tarp from flapping as much in the wind and less noise equals better sleeping.