Are you wearing enough to keep your core warm? I generally stop cycling this time of year, but I do spend a lot of time outdoors (mainly cross-country skiing). I've found that if my core is warm enough, the rest of me is too (hands, feet, face etc).

Booties can be extremely helpful for blocking the wind and keeping your feet from cooling off too much.

The other thing to think about is how tightly your shoes fit. You want to wear a warmer pair of socks, but be careful you don't get so much in your shoes that the circulation is impaired.