Montana whitewater rafting clothing?

I'm going on a whitewater trip in late July. I've never been to Montana, and I don't know the weather conditions. Obviously the goal is to stay warm and dry either way. Aside from neoprene gloves and water shoes, how much do I need to dress for the occasion? The full 9 - full wet suit, fleece, and rain jacket? Shorty wet suit, board shorts, and a long sleeve rash guard? Category 3-4 water. Thanks!