A couple of years ago, when The Excellent Wife (TEW) was in Krakow on a language-immersion experience, I built up a Surly Crosscheck frame into a bike I call the Krakow Monster (well, TEW was in Krakow, see?). (For the ridiculously curious: parts, lacing the wheel (complete with dumb mistake), turning the dining room into a bike shop, the front end, fitting the cranks and cassette, completing the drivetrain, and finishing up.) It's the most versatile bike we own, and it may be the most versatile bike I've ever seen: I've taken it on Hill Slug and other club rides, I've led slow rides with it, and I've taken it for chores. It has a compact 50x34 in the front, and the big cog in the back is a 34, which means I've got a 1:1 low gear (sometime Hill Slug Peter G calls that "tricycle mode", and looks on it with disdain).
It's now sporting fenders and a rain-resistant pannier. I took it out this morning in the weather (initially drizzle, later real rain) for the three-mile-or-so round trip to the local post office (we actually live close to the post office in a neighboring town); the pannier kept the mail dry, and the fenders kept me dry - well, dryer anyway than if I hadn't had them. (I learned years ago that the real wet from riding in a gentle rain comes not from the water from above, but from the water splashed up from below by the tires, complete with road grit and other filth too gruesome to mention.)
Fenders notwithstanding, I'm claiming Rule 9 for this ride: "If you are out riding in bad weather, it means you are a badass. Period." I see that a number of scheduled rides were cancelled. I was out. Granted, it was short, but I got pedaling in.
(By the way, if you're on the fence about fenders for one of your bikes, remember that they also help to keep the rider behind you dry. If you're in a paceline on a wet day, you'll get a face full of the aforementioned road grit and other filth. The control of this disease vector is surely a corporal work of mercy, doncha think?)
(Oh, go look it up.)