Blocks that are able to be submerged in water, and able to be walked through can have rain fall through them (And the sea cucumber can as well). This graphically annoying sense rain appears to go through water. Slabs don't have actual stripes of rain falling through them but instead still have the actual rain particle spawn, which is still a bug. Trapdoors, when placed with their horizontal state at the lower part of the block, also have the rain particle spawn (The one get with the /particle command). I have included some images below regarding the bugs.
To reproduce place on of the former mentioned blocks to see either rain itself, or the particle of rain, going through the block or appearing on the surface.