The last time we were there we went late July early August, and I must say some days were VERY hot. They felt even hotter for us coming from Seattle. I dont think the heat wore us down as much as the humidity. Have you ever been in a green house with no breeze? Thats Florida. When you walk to your room at some of the resorts, you can smell the mold growing. The afternoon brings massive breezes before the rainstorm, and no, the storm does NOT cool things off, but it does help. The parks empty out, and teh breeze feels FANTASTIC! Lets all hoep they extend the hours because if so, after or near dark is the best time to avoid hot heat!!So sleep late, and hit the park late. One thing you will learn to appreciate are the sunsets. My husband is from Phoenix and I have seen pretty sunsets, but some of the storms are the best I have seen.
BTW, the week we went, it was about 92 degrees, with 96% humidity. But hey, it couldnt have been that bad, we go again in August!