We had 8-10 boys in that cave. I remember it was a bit cold, but not unbearable. I don't think I had a good enough pad to insulate me from the ground.
This was in the flats just below the Pomerelle ski hill near Burley, ID. Snow was probably 3 ft deep. We all brought shovels, and we piled up snow into a pile about another 3-4 feet above the base snow level. Tromped all over the pile, then dug down to ground level and started tunnelling in to the pile and basically hollowed out the pile. Once we got it hollowed out we were careful not to walk on the roof. I remember that a short 12 yo could stand up in the center.
Our Scoutmaster slept in a tent nearby.
The next morning after all gear was removed from the cave, we tromped around on the roof and it held up t all tromping and jumping. Then we cut a hole in the center of the roof (it was about 1-1.5 ft thick) and lit a fire down inside the cave. It did not draw well, so the cave just filled up with smoke.
Probably a huge violation of safety protocol (e.g., a cave-in could have been dangerous), but back in the 80's we lived dangerously.
Also, we should have finished first in the Klondike Derby race, but came in second instead. We had one laggard that should have been able to keep up... but wimped out and didn't push himself like the rest of us.