We were there that time this past May/June. It rained every day we were there, so that kept people out of the parks. It was only a heavy enough rain for about 1/2 to even need ponchos, so fine with us. It was about 85-88 degrees so it was warm enough to be wet outside. We walked on to pretty much every ride from the time we got there until about 1:00 in the afternoon when the rain quit, then the lines were about a 50 minute wait (which we discovered was about 10 minutes off--so they were about 40 minutes in reality). When we were planning for our trip I looked at the temps from the previous year and it was 95-100 every day we would have been there, so you never know.
We though it was funny when we saw people at the waterparks, wearing their swimsuits, wearing ponchos.