When it's below 30F, nothing retains head heat like a balaclava.
I misplaced my neck gaiter thingy that I'd normally stretch over my head, which fits comfortably inside my helmet, so I grabbed the next best thing—or so I thought—my son's balaclava. The sizing was a bit snug, but I'm sold on it's design to cover my face and neck! I'll have to unearth my old balaclava—one I've had for 30 years —and adapt it (if I recall it had extra material that formed a widow's peak, partially blocking my vision) for use on the bike.
Between windproof mittens, a balaclava, and Ugg-type boots, I'm learning how to extend my riding season.