Riding in rain is a fact of life for the rest of us. Though those of us who don't live in Seattle will try to avoid it. How much is it supposed to rain?

No, it won't hurt your bike. Clean your drivetrain and brakes when you get home, though. Your clothes and shoes will dry. I'd say leave them out in the sun for a bit, but I don't deal with the beasties that you have to! If you don't have fenders, you may end up with dirt/mud on your back from that "rooster tail" if it's heavy rain. It'll wash out.

Wear what you normally wear, with an extra layer. (I rode 30 miles in rain this summer and was cold and unhappy for the last ten miles.) Perhaps a shell with pit zips.

Riding in the rain's a lot like driving in rain. Give yourself extra time to stop, and take turns slowly. Also, if you're in a bike lane, you may well end up with a nasty mess on your hands because of your lack of storm drains. (DBF lives in your general area. He tells me these things.)

It can be a lot of fun. Just be safe.