Category:English words suffixed with -phile from Wiktionary.
Both your terms happen to be defined there:
pluviophile – Wiktionary : (biology) Any organism that thrives in conditions of heavy rainfall; One who loves rain, a rain-lover (from Latin pluvia)
bibliophile – Wiktionary : One who loves books; One who collects books, not necessarily due to any interest in reading them. (from Greek biblion)
If you know a bit of Greek or Latin (or Italian), you can work these out.
Why are they not in your Oxford dictionary? Depends on your Oxford dictionary. There’s lots of vocabulary that is considered obscure, specialised, or antiquated, and the smaller the dictionary, the more of that kind of vocabulary it gets to exclude. I’d be surprised if pluviophile gets used seriously now outside of biology, and within biology it may be antiquated. I’d have thought bibliophile is slightly less obscure, but I’m not writing marketable dictionaries.