Survived two nights in a 4 person snow cave on Mt. Rainier, at around 5000' and 15 degrees F. First one was not so hot, as I got super wet in the digging process. I was the main digger, and others shuttled snow out. A tough team effort. Snow caves are supposed to get up close to freezing from body heat and insulating snow.
Breaking it down in the end was educational. Even though the ceiling has slumped about 6 inches over the two nights and one day, it was still hard to break. We cut it away to study the snow layers, and icing up of the ceiling from breathe and water vapor off our wet clothes. It still needed a lot of jumping to collapse the roof, which is reassuring. None of us had done it before.
My wife was getting claustrophobic as we dug it, but got through it. I was not into venturing out into the wind, soaked through my shell layers, to the close-by car for the tent through the wind, but would have.
<a href="http://www.flickr.com/photos/southsoundtree/5319917385/" title="Amy and I, partially deconstructed snow cave by South Sound Tree, on Flickr"><img src="http://farm6.static.flickr.com/5130/5319917385_8110fbe152.jpg" width="375" height="500" alt="Amy and I, partially deconstructed snow cave" /></a>
Robert, Sarah, and Amy ahead of me, up on a ridge during our daytrip. Robert was overheating from "skinning up" on his telemark skis. The three of us snowshoed. I left my skis at camp to spend the day doing the same thing as my wife, rather than skiing with Robert.
<a href="http://www.flickr.com/photos/southsoundtree/5319916637/" title="Robert Sarah Amy on Mt. Rainier by South Sound Tree, on Flickr"><img src="http://farm6.static.flickr.com/5249/5319916637_191106de49.jpg" width="500" height="375" alt="Robert Sarah Amy on Mt. Rainier" /></a>
The top of snow cave entrances are meant to be at least 6" lower than the floor, helping to trap the warmed air within. 3 vent holes were poked through the 2.5-3' snow ceiling with an ice ax shaft then ski pole with basket. One is seen top left.
<a href="http://www.flickr.com/photos/southsoundtree/5320517542/" title="snow cave entrance tunnel by South Sound Tree, on Flickr"><img src="http://farm6.static.flickr.com/5122/5320517542_c967e814ce.jpg" width="500" height="375" alt="snow cave entrance tunnel" /></a>
Here's Sarah waking up on the far side of the cave, with the picture shot from the other far side.
<a href="http://www.flickr.com/photos/southsoundtree/5319915599/" title="Sarah waking up on far side. by South Sound Tree, on Flickr"><img src="http://farm6.static.flickr.com/5209/5319915599_80c14087aa.jpg" width="500" height="375" alt="Sarah waking up on far side." /></a>