I live in Seattle like Marquezdl and my moto jacket happens to be water resistant. My sneaks are too, as is my backpack. Do you wear protective gear? If not, just buy a protective jacket that’s water resistant/proof. If you already have gear then just get a pocket unfoldable one to slip over it. Just don’t store it under your seat, that sounds like a real pain in the ass to get out every time it rains.