Best I've found is a trapper type hat with real rabbit fur. Keeps your head and cheeks warm during the day and at night you undo the front flap so it covers your eyes and nose. The fur fluffs around your mouth but resists getting cold from the moisture in your breath. Make sure to spring for the real fur unless you are opposed to that. It makes all the difference in warmth. You can get them on sale for twenty bucks.