https://thunderstore.io/c/lethal-company/p/ButteryStancakes/FloodedLevelsFixed
This mod fixes a bug with vanilla that causes Flooded weather to not work unless you land there on the first day of a newly hosted session.
This mod is server-side and only the host needs it installed (it won't do anything as a client unless the host has the mod too)
More technical details available in the mod description if you are curious as to the cause of the original issue