About 12 years ago I was working as a wrangler for a sheep hunting outfit in the Rockies in. A fellow in camp decided to shoot an elk across the Smoky river. Said fellow was not only a major PITA and moron, but also deathly afraid of water. S, it fell to me and another wrangler to go butcher and retrieve the elk.

It was still early enough in the day that we figured to be back before dark. We should have known better. The river is deep and fast, and it took us several hours to find a spot where the horses could cross. Even then, it was a near thing. We backtracked down the other side of the river till we found the elk.
We got to butchering and packing it on the pack horses we brought. It was getting pretty dark as we headed back. Before we got back to the crossing, darkness fell and for once, the horses did not seem to know their way back. We ran into one pile of deadfall after another, and finally had to admit we weren't going to make it that night.

We made camp on a small island in the river, to hopefully avoid the grizzly and wolves. The same numbnuts who shot the elk had sat on the stock of his rifle while accompanying us down to the river and broke it. I loaned him mine to ride back to camp, figuring I'd be back in plenty of time. We built a nice big fire and settled in for the night. At first it wasn't too bad, but it started getting seriously cold after a few hours. I used a horse blanket for cover, which didn't smell great but helped some. Not much sleep was had that night, but I did get to see what was easily the most magnificent display of Northern lights I have ever seen, it was absolutely spectacular.

I was well below freezing I'm sure but how cold it was I couldn't say. I've slept in far colder, but never been colder at night than I was that night. Learned my lesson, for sure.