Get warm gear, especially gloves. I commuted until early December last year, and started up again in March this year. I still rode a few times in January, but didn't commute. You have no idea just how cold -5*C is when you add a 130km/h wind chill factor. I wore gauntlets, and even tried snowboarding gloves, in the end I had to give in to the cold. My commute is almost an hour each way at highway speeds.
I rode when there was no snow on the road all last winter. The gloves are a major thing I found that i needed to improve, then helmet, then pants.
My current winter gloves are Joe Rocket Nitrogen, water "proof" and warm, with a little bit of a gauntlet also. I went to the Bike show in February, a trip maybe 75 minutes long and had to stop twice to warm my hands; i was on the 403 for most of it and i think it was -10. I'm looking to get Gerbing T5 heated gloves this year.
My helmet is an Icon Alliance. Amazing in the summer, but not fantastic last winter. It has a lot of venting and an anti-fog that doesn't last too long. I'm trying to find an inexpensive replacement with a pinlock.
If you can tough it out in the negatives with the gear you have, then go for it. There's a potential for a number of clear days with plowed streets.