Timber rattlers are as far north as upstate NY....I actually saw one Minnewaska State Park a good 5 years ago...Where the heck do they go in the winter...Cold blooded and NY winters???Wierd combo if you ask me
Timber Rattlers are listed as endangered in NJ due to loss of habitat - as the most densely populated state in the Union, that is no surprise.
They hurt when they bite, I'm told, but they are not particularly deadly. Their venom is less deadly than western rattlers. They usually bite when disturbed, and like to hang out in the piles of leaves that accumulate at the base of rocks and logs.
As far as reptiles living in cold climates, there are numerous examples of successful species that live in cool climates. Aestivation (sunbathing) is seldom done in winter. They just hibernate in holes or cracks in trees. I've seen more than a few snakes in Maine in the winter.
Sorry for the Wikipedia moment. Naturalism is a sort of hobby for me. Good thing no one has brought up Wild Edibles and Plant Identification yet...