I was at MK once and it rained all day. It wasn't bad as there are alot of rides inside. However, there are some that are outdoors and well, you just get wet! The good thing was that it scared away alot of crowds. The way we looked at it was, well, we are here, we're not going to let the rain stop us. We're going to have fun anyway. I think though, MGM may be better if you know it's going to rain. Most everything is indoors. You'd just miss Fantasmic if it rained in the evening. I shouldn't say "just" as that show is awesome!