Checking the current conditions after class yesterday, I saw that what I wore in would be inadequate for the ride home. So I added a merino sweater I keep in my locker to wear around campus and was comfortable.
It didn't get as cold as forecast last night, and it was -4C for the ride in, my water bottle didn't even start to freeze. I used my thermal tights, shoe covers, wool gloves and balaclava and was sufficiently warm. With all the water main breaks lately, I need to start watching for water that turns to ice overnight. Yesterday someone was asking me about the bike cage since they also want to bike through the winter.