In Vancouver most roadies have a "winter bike" and I'm sure Seattle is the same. Fenders on both wheels are quite important here because the road is very gritty in the middle of the winter, and all that junk will end up in your drivetrain if you don't have the fenders on. They also spare your behind (you don't want to look like a skunk, because as we now know it can get you killed!!!) and saves your riding partners from having their mouth full of muddy water.

I don't have a winter bike but I do put fenders on, and my wheel hubs are sealed.

If you ride on relatively clean roads, and don't mind the very dirty laundry, then proper lubing and cleaning will be sufficient. Make sure you wipe your bike when you get home, and wipe the chain to remove the gunk if necessary. Assess the damage and clean if necessary! But truly a ride in the rain happens once in a while no matter what, so don't worry too much about it!