I'm currently on Xbox One and I noticed when it started raining, my frame rate dropped to 5 frames for seven seconds then the frame rate went to 50 frames. Rain still does affect my game performance regardless of my graphics settings, but it's not as bad as it used to be.

The issue related to water causing game unstability has been fixed.
If it matters: I'm on the Xbox Beta update which I noticed is really buggy at this stage. (I'm in the Beta update ring, right next to Alpha update ring)