I used to winter camp/back pack with friends. My wife was smart enough to always be too busy with the kids after the first time she went. I never made a snow shelter, and always used a small dome tent. With two people the are 10-15 degrees warmer than outside, with three people we ran into a number of problems. It was -20F with estimated 15 to 20 MPH wind. First; it looked like a Laurel and Hardy film, when we set up the tent the first night, we all turned to grab our gear, of course the wind grabbed the tent and blew it like a tumble weed. I went after it in 2 feet of snow and caught it after about 100 yards, carrying it back was walking into the wind with a 7' beach ball. We got our gear in it and bedded down for the night. I never figured out if the heat from our combined bodies melted the snow or/and the condensation from our breath, but we had 2" of water in the tent in the morning and the tent was sunk in the snow about 12-16" from where we started. Everything went pretty normal for the rest of the trip until the last morning. We knew a warm front was coming, and needed to get an early start hiking out. One of the guys just puttered around and we were an hour or more late braking camp. There had been about 1 1/2" of powder snow during the night and it all stayed on the limbs. It was one of the worst beautiful sights I've seen. As we hiked through the woods the heat and sunshine melted the overhead snow and it fell on us. Numbnuts was in the middle of us, so every time we went under a snow laden limb one of us would kick the small tree to dump the snow on Numbnuts. It took 2 1/2 hours of almost running to get free of that mess and all 3 of us were soaked to the bone. at about 25 degrees F. Fun times! Ivan
PS For the trip my wife and I went on I bought each of us a Semi mummy bag. Hers was a large with a right hand zipper and mine was an X-large with a left hand zipper. They mated up fine and we slept very comfortably at about 5 below 0 F, and have used them on cold weather outings since. I have used mine to about 20-25 below in the tent. Ivan