Living a little inland, I recall feeling really cold on a downhill at 43 degrees. Makes race bikes difficult in January, since all that stuff will be unneeded by 10. Problem is where do you put it all.
Layering is a good plan. At 43 degrees, a light jacket almost seemed to work if you had on multiple layers underneath. I quickly notice the cold about my hands , feet and neck. I suggest thermal t shirts might work almost as well as a winter jacket? They can be purchased with long sleeves.
Guess one solution is to start you ride at 9:30. Hated January tho, seems fog might last until almost noon couple days a week.
43 degrees in Minnesota in January, you'd have nudist swimmers jumping into the lakes though holes in the ice.