Nothing changes except the sunlight and how many layers you wear. Don’t let a little cold make you eat things you know you shouldn’t. There is some truth about how light/cold affects what you actually crave to eat, but still, no reason to completely fall off the wagon, that’s extreme.
I started Primal the last week of January, it’s about to be a year for me and it was just getting cold. I still made all the dietary changes that I more or less have kept till today.
Use opportunities such as shoveling to get your exercise in, stuff like that. Hope that helps.