Rivendell sells a rain cover for Brooks saddles. Also while Proofide is great to use, too much can create a problem by over softening the leather. You should only use a small dab and rub in real well, after that you shouldn't have to reapply it again for a year. I have also used a neutral shoe polish wax to seal the leather. I do use the seat cover though if I'm going to ride with the possiblity of being rained on.

One thing to remember about Brooks saddles: if you use any other leather treatment other then Proofide your warranty will be voided-this does not apply to wax.