Depends on whether I'm actively moving or sitting still!

When I'm actively hiking, just a headband (Smartwool) is plenty enough. Otherwise I get too sweaty. I generally wear just a medium weight baselayer top and wind shirt, plus perhaps a lightweight fleece vest, when I'm moving. When I'm sitting still, I have a fleece balaclava, a puffy jacket and often my rain jacket (the only jacket I have with a hood).

Just a note: Here in the Pacific NW, winter temps are generally in the 20s or 30's and it's just as apt to be raining as snowing. Of course we occasionally get ferocious east winds out of the Columbia River Gorge which send wind chill temps down below zero, in which case it's bundle up in everything I own when outside and curl up by the wood stove the rest of the time. It's well known in the Portland area that residents of Troutdale and east Gresham can be spotted by their permanent lean!