There were a lot of questions last fall about this topic posted on here. Almost without exception, the answer was always "they're fine." Several posts from folks in very cold climates -- MN, ND, even Alaska -- all said that even in those climates there wasn't any problem.
Since the birds live wild in quite northern regions, I guess they are adapted to it.
Also, very few people altered the normal routine. Most said the turkeys continued to roost in the same place year round no matter what the weather.
The only thing different you will definitely need to do is provide an unfrozen water source, such as a heated bowl.
Some people also feed cracked corn in addition to the regular turkey pellets, feeling that the high carbohydrate level somehow "heats" the body more. I don't know if this is true or just an old wives tail, but the Chinese do categorize most foods as either "heating" or "cooling" to the body, and often adjust the diet seasonally based on this system, so it may well have some merit. Certainly won't hurt anything.