How cold are you thinking? Winter touring? Personally I wouldn't plan a tour where the weather is expected to be sub-freezing for much of the trip. I think there are more fun things to do in the winter than be on a bicycle. Backpacking, trail running, skiing, snowshoeing, etc. are all more pleasant in cold weather than being on a bike IMO. That said you need to be ready for some cold weather in the higher mountains no matter the time of year. In that case I would tough it out with double socks and plastic bags on my feet.

I usually try to camp lower when it is cold up high and if possible hit the passes in the warmer part of the day.