I believe June-OCT is considered hurricane season, so you are fair game any of these months. I personally was there in Sept 99 during Floyd in which parks were closed. This was the only time WDW closed due to a storm so your chances are pretty good I think, of avoiding an actual hurricane. Rain is a different story. It pretty much rains everyday in the summer, but mostly just a 1/2 hr downpour, then it's sunny again. If you are concerned, buy trip insurance and watch Orlando weather before you leave, so that you can reschedule.