How much can humans adapt to the weather/climate?
Many years ago, I read about the studies the US military did - as part of the NASA space program. They wanted to know just how much people could adapt to. I still remember two of the studies. One concerned how much heat people could live with/in. The other was how cold.
They took a family of 4 (man, woman, two kids), put them in a private/seclude home. The heat was turned off, the windows were permanently opened, the people had no clothes, and they were only allowed a sheet on their beds at night. They started the study with the family in summer - so the transition to the outside climate was pretty easy. They then followed the family's progress as they moved through fall and on into winter. The last picture (discreately posed) showed the family sitting out on the patio eating breakfast while sitting in snow! They were exposed to the outside climate 24 hours a day, every day. They got acclimated to it. But the researchers did note one minor side-effect: a slight increase in body hair!
The other part of the study was to see how hot of temps a man could adapt to, and for how long. They started with a large "oven" or heat chamber, and had their volunteers sit in it. They ran the temp up to 100, and had them stay in there for an hour, and then slow-cooled it back to normal. Of course, their test subjects were carefully monitored before/during/after each session. The next time they cranked the heat up a little higher. In the end, they had several people that got "acclimated" to some pretty high temps. The last temps they reported were 1 hour at 300 degrees (F)!!! The guys lost about 10 pounds of water in sweat, but suffered no ill effects. 300 degrees (F) for an hour? That's what you do when you bake supper in the oven!
So people can adapt or acclimate to some pretty extreme climates. Just look at the pictures of all those Eskimo kids running around nekkid in their igloos while playing on the ice floors! My folks remember when they were growing up on the farm - they would occasionally run around playing and doing chores barefoot in the snow. I heat my home with wood, and get ... acclimated ... to much cooler temps than the rest of my family with their modern central heating systems. At family gatherings, I'm the one shucking off clothes while they are turning up the thermostat and complaining about being ... chilled.
So most of it is what you get acclimated to. And then you need to really know the area you are in. After that, it all depends upon your skills.
The other thing to keep in mind is that it is a whole lot more than just keeping warm overnight. You also have to find a source of water, and secure a food supply. A lot more knowlege/skills to blend into your whole experience. Being trained from a very early age to do all this really makes it a lot easier to do.
Just some more humble thoughts to share. Take them as such.
Mikey - yee ol grumpy blacksmith out in the Hinterlands
p.s. I need to find that NASA study stuff again. It had a bunch more stuff they studied - like adapting to always being exposed to light, or to near dark. And how to tell time without clocks or seeing the outside. (Most of the subjects eventually settled on a 26 hour day instead of 24 hours! What's up with that?) Yeah, that was an interesting article/report - if I can find it back.