Happily, I have some waterproof pants, thanks to a very generous and committed-to-4-season-cycling friend, and so I put them on as I left the school last night and rode off under suspiciously dark skies.
It was a good thing I decided to wear the pants. Within 10 minutes of riding, a light drizzle started, and not long afterwards, big, heavy drops rained down on me and my shiny, new bicycle!
By the time I got to my destination, it was pouring. But I was dry as a bone, as was my iPod, which I continued to listen to while riding, to motivate me along the wet streets, and which also stayed dry thanks to a waterproof, bike-mountable little gadget/cover thingie my friend had given me only the night before! Perhaps the best part of the ride was the funny looks people gave me out of the enclosed comfort of their cars as I rode by -- a sort of mix between confusion, pity and "are you insane??!!" -- little did they know how enjoyable riding in the rain can be.
With the right music in your ears and the right gear on your body, I believe one can commute by bike year round. So far, I'm in!