Reptiles are cold blooded, so they adapt to the temperature they are at, as I remember.

and there are plenty of snakes here. My landlord got bit by a rattle snake and I had one in my livingroom in October, it was getting cooler and he was looking for warmth I guess. Lots of Bull snakes, good mousers.

is that snakes do not survive the higher latitudes.... I know in Colorado they hibernate in winter, but even in warmer months tend to stay in the lower areas and not in the more mountainous areas. I would presume the same to be true of the Dakotas and other colder climes. What gives us a startle is after an unseasonably and early warm period, they start coming out, even in the winter--something that we may be seeing more and more frequently with global warming. Homeowners are most likely to encounter them in the fall, when they are looking for somewhere to hibernate.