Well, considering it was snowing at higher elevations when Rowan and I were in Switzerland a couple weeks ago (and doing the cold rain thing down in the valley where we were cycling), there could be a chance of snow along the way, depending on the height of any mountain passes you're thinking of tackling and the time of year you get there.

Another thing to consider would be campgrounds. If you are planning to use campgrounds, some are open year round, but we've checked a few here in the Bordeaux region of France, and they close in a few days.