Found the text below on this web site
http://www.tripadvisor.com/Travel-g34515-s208/ Orlando:Florida:Weather.And.When.To.Go.html
Unless high humidity, afternoon thunderstorms, and masses of hot and sweaty tourists sound like your ideal vacation, then avoid Orlando in the summer months (June to August).
Certainly, a visit during this time frame just calls for a revised game plan. Wake up as early as possible and hit the theme parks as soon as they open. The early jump on the day will help with both the weather and the crowds a bit, and if you plan your day right you can get out of the park by early afternoon (before the thunderstorm hits) and go for a late lunch, take in an afternoon movie, or do something else indoors (like DisneyQuest). You can then return in the evening, when things have cooled down, to enjoy the summer's expanded slate of entertainment, nighttime spectacles and fireworks shows.