Skeleton stay under tree during rain time

Skeleton stay under tree during rain time and don't run after me.

What I expected to happen was...:
The skeleton run after me to kill me.

What actually happened was...:
The skeleton stay under the tree. (If i break the blocks over his head, he run after me again.)

Steps to Reproduce:
1. Spawn skeleton under tree or any other blocks in the day
2. Put weather to rain
3. Change to gamemode survival, the skeleton shoot you but stay under the tree, he don't move.