I know bikers who shudder at the idea of riding in 40-degree weather. "Oh, that's too cold!" they say. Well, cold is relative.
Today's bright sunshine lured me out into 20 degrees. Aside for ice patches, the only real problem is your helmet fogs up. A cure for that, opening the visor, is worse than the disease -- blasts of arctic air freeze your face like liquid nitrogen. Oh well... YOLO.