After you reach 95 or so, what does it matter? July feels just as hot as August. I've been twice in July and it's terrible. I have a picture of my cousin's ds at 7:30 am waiting for the monorail - there's sweat dripping from him. It was 90 degrees and humid (yes at 7:30 am). Make sure you wear lightweight, light colored clothing and drink water constantly all day to keep from getting dehydrated. You will be thankful for the frigid AC in the attractions, gift shops, and restaurants.
And we only go in the off season now after that last trip.