I also had my combat get stuck, and it was indeed on a turn where I used the rain spell if I remember correctly.
With "got stuck" I mean that the interface was responsive, but clicking "end turn" had no effect.
After clicking "End Turn" and hitting all kinds of escape etc. keys, the fight continued after a long waiting time (I had almost given up at that point), but then all of my other characters turns got skipped.
It looked like the game was executing my "end turn" commands, albeit after a very long delay.