Comment by emptybottle

A good reminder to keep some warm blankets/coats/gloves/hats in your trunk, along with some non-perishable snacks and a first-aid kit & flashlight.

Water is harder to store in the winter since it will freeze and burst containers if full, but snow can be melted given a container to put it in.

Also a good to refuel often. I try treat 1/2 a tank as empty and stop accordingly. On longer trips it lines up well with bathroom breaks.