As a adult male that is follicley challenged, I find the wind and rain protection essential. As a result the Pearl Izumi skull cap the perfect barrier for under the helmet winter rides. It is cut to provide a bit of wind protection as well. It was My riding companion for all coolish rides.
This skull cap does a good job of keeping my head warm in cooler temps down to the 30s. It fits nicely and blocks the wind as well as any other cap Ive had. I only wish the sides came down a bit lower to cover my ears fully. The current design only covers half of my ears leaving them a bit cold.