Just to be clear, are you trying to argue that MitD caused the rain in general, or that he only was able to cause the rain at that point in time because the cloister effect on O'Chul let up?
Edit: I'm still not clear on what the point is, but the answer will depend on what ability MitD would be using, which will itself depend on what MitD actually is. Some would be affected by cloister, and some wouldn't.
Grey Wolf