Rain appears to travel through transparent blocks (stairs and slabs especially).

Put the summary of the bug you're having here

What I expected to happen was...:
Rain to not travel through stairs and slabs in my ceiling.

What actually happened was...:
Rain was travelling through the stairs and slabs in my ceiling despite no actual open sky being visible.

Steps to Reproduce:
1. Place slab or stairs above an air block.
2. When rain occurs, it will travel through these blocks.