September in Florida you do have the risk of tropical storms, but in Central FL, the risk is pretty low. I would not hesitate to plan a trip in September from that perspective. The weather in September in Central FL can be pretty brutal if you aren't used to heat and humidity. I'm from Florida and live in Georgia and even I was a little grossed out at how quickly and how much I sweated on my trip this past September. That said, many attractions are indoors or at least under coverings with fans going. You can get free water at any time from any quick service food location. If you stay hydrated, it's really not that bad. Again, wouldn't hesitate to plan a trip in September. Low crowd times like I remember from the late 90s and early 2000s do not exist anymore, but September is still a relatively low crowd time. By Labor Day, all schools are pretty much back in session and it's early enough in the year that not too many people are pulling kids out of school for family vacations. While the weekends were pretty busy, we found the week days much less so and quite enjoyable. If you can handle the heat and humidity, I think it's a great time to go.