I'm currently living in Tokyo and at a different point I lived in Germany. In both these places, and a lot of the rest of the world, people bike commute year round and don't own cars. Some things I've noticed in Tokyo are waterproof covers for the kids seats and handle bar baskets as well as Poogies (built in hand covers). Also, a lot of people here have electric bicycles. You'll see women riding around with one kid strapped to her (baby bjorn style), one in the front basket and an older kid in the back child seat. These bikes cost about $1300 US in Japan, but I haven't seen them in the US. MMM has a recent post on converting your existing bike to electric. There are other trendy brands of cargo bikes like Surly's big dummy or XtraCyle and Bern, but they are pretty expensive (new).
In Mpls (my real home) some people bike commute all year long through sub-zero temps. The key is really figuring out your layering systems. The cycling infrastructure is way better outside the US, but there are still plenty of people riding year long in tough climates. Try finding cross country ski gear (lobster gloves so you can shift and break) and googles. Make sure you have waterproof or at least warm shoes. Use news paper bags to cover your feet for wind block and get a waterproof bag or paniers to carry a change of clothes and anything you need for work. I have some friends who have retrofitted the kitty litter buckets for use at Waterproof paniers which works well.
Also, check to see if there are rentable bike storage compartments near your office. In mpls there are nice lockable boxes to store a bike that are cheap $5/month or so and can make it safer to store things instead of lugging them around everyday.