-21C just outside Toronto this morning. Since I have a short ride to the train station I just used my regular layers & balaclava (the thine one) but if they commute was going to be any longer than 20 minutes I really recommend the overpants & goggles, I was definatetly freezing my eyeballs as I pulled up to the bike rack.
Good thing about the really low temps is it makes you appreciate the warmer days.
Stay warm people! (outside of you Southern Hemisphere people...how's summer doin' down there?)