Snow tires should really be called winter tires, since they have a different chemical makeup and stay soft (to grip the road) in cold temperatures. Any time temperatures are consistently below 7C (45F) you should have winter tires on the car. Here, and I am guessing in Maine, that means all winter. They are fine on dry roads, there is no damage. They do wear out faster when it is warm. If you plan to keep the car for several years, it is worth while investing in winter rims as well. Once the tire is on the rim, it stays there permanently, so less wear. At the change of season you just pop one set of rims off and put the others on. Ask your garage when to get them on and off, or just look at the long-term forecast. Here in Eastern Ontario, and when I lived in South-western Quebec, mid-November was the start, and some time in April was the end.
Quebec passed a law a few years ago making winter tires mandatory between mid-December and spring. Apparently accidents caused by winter conditions are definitely down.
AWD does nothing for driving on snow, I learned that the first December I drove an AWD Subaru. We had a snowfall before I had the tires changed, and I had no grip. Slithered like mad even at slow speeds on a small hill. I do fine in a Mazda3 with snow tires. Most of the time I am driving on clear dry roads. Even driving home in a blizzard last winter, I had no trouble holding the road. My problem was visibility, and figuring out where the road ended and the shoulder started. There was at least 2" of snow on the highway, and more in places from drifting. And that was on tires that will not be going back on this fall.