Dude, your head is so cold right now. most of your body's heat escapes from your head, and there you are unprotected, like a chump.
We would really rather you were all bundled up on these cold winter days, your beard will protect your lower face, but what about your dome? you need this knit beanie hat badly. Our neighbors to the north call this a "toque" and quite frankly, i think that is a better name for a man's hat than "beanie" so, going forward, we will call this a toque.
and you should get one.

one size fits most human sized heads.