Rain particles are not stopping and bouncing when hitting the highest y-level block in a given x/y co-ordinate, and instead continue to fall through blocks all the way to bedrock. Attached is an underground location at roughly y=11 with rain particles breaching the ceiling as if it were above ground. Another screenshot shows the rain particles descending through blocks in spectator view.

I have tried reloading chunks and leaving and re-entering the world, neither of which have fixed the issue. The world was created pre-1.16 snapshots and functioned as expected prior to this snapshot (20w17a).