Meh. I don't use a helmet in the winter. The risks of winter head trauma are smaller for me, I have a soft beanie and other hats when needed.
Fitting enough head gear under a helmet and covering places that matter is, I find, next to impossible. Also there is the whole forehead issue. When it gets to -25° C I need to really cover my forehead with a special beanie and buffs etc.

Also, my beanie is a hair styling device in the winter and a helmet cramps that up too much.