I live in the Rocky Mountains at about 10k feet. LOTS of snow. Long winters. I built my own insulated coop and ran power out to it for a couple heat lamps that i turn on when it is really cold. Even when it is around zero outside the coop stays about 45 degrees. I put up a large loafing shed attached to the coop that is open on one side so the chickens have somewhere without snow to walk around in the winter. Also the coop is elevated about a foot and a half off the ground. Giving them somewhere to hide from hawks and the elements. The bigest challenge is keeping their water from freezing. I recommend using rubber bowls so when it freezes you can stomp the ice out and refill. You would be suprised how hardy chickens are but i try to keep them as comfortable as reasonably possible. I know someone who keeps a flock up in Alaska. They can thrive anywhere with a little acomodation.