Interesting article. One other thing I noticed on the really cold night of camping was the air inside the tent also got really cold, so simply breathing in the cold air seemed to sap the heat right out of me. Added to that, every time I moved cold air seemed to rush inside the sleeping bag (or the air I had warmed with my body rushed out, either way, brrrr) made the night really miserable, even with 3 layers of clothing on. Dry synthetic long johns, fleece shirt and pants with wool socks and a hat on my head, and I eventually added insulated coveralls to get through that night (and yes, all were fresh and dry). How cold did it actually get? Hard to say for sure, i know it got below freezing as there was frost on the cars, tents, equipment, grass, and everything else that was outside the tents.

A few other things to note, the sleeping bag I used is a rather normal rectangular design, seemed well insulated tho it is an older bag we bought a while back so I suspect it's rating was less than adequate. DS and I slept on 4 layers of old comforters (2 blankets each, folded in half) with the sleeping pad on top of that, followed by a fleece blanket and then the sleeping bag (with two of those chemical handwarmers inside) on that, with the foot of the sleeping bag covered with a large contractors bag and all covered with more fleece blankets. DS seemed to tolerate it better than I did, and with temps expected to be close to the same for the next weekend's campout, I went and bought us some cots to sleep on, plus the fleece sleeping bag liners and the full size chemical hand and body warmers. I guess it was a combination of all of those and maybe the temps not getting nearly as cold, but that next campout, with the same sleeping bags and blankets we had at the previous one, was much more tolerable.