Keep in mind, often, it doesn't rain for very long in Florida, especially in the Summer. Usually, you can see the storm roll in and watch it leave the area all within an hour. Unless the forecast is for rain all day, always try to wait the storm out. You will make up the time you will lose waiting the storm out afterwards because the park will be almost empty, or at least much lighter attendance wise.
Of my few dozen trips to Florida, only once did weather ruin my trip. We were there for a week in April about 15 years ago. It rained all day, every day, except one. The local weathermen got a real kick out of it. One guy opened the morning weather segment every morning with, "Sorry Spring Breakers". I can still hear his voice and I still hate him!
Remember, everyone wants a sunny day at the parks. And that's the problem - that's when everyone goes and the parks are jammed.