On my way to looking up something else (I'm one of those people who gets easily distracted by the pages of an open dictionary), I found a word that's new to me: pluvial. My dictionary defines it as an adjective, "of or pertaining to rain, esp. much rain; rainy," but I also see in an online dictionary (Merriam-Webster online) that it can be a noun, a "prolonged period of wet climate." (Sounds like a synonym for Seattle.)
If you like the sound of pluvial, you may also like its rhymes fluvial (of or pertaining to a river) and alluvial (of or pertaining to alluvium, which is a deposit of sediment formed by flowing water).
Any other fun water or mud words I should know about?