It's hurricane season, it's Florida it's most likely going to at least have a short afternoon shower at least one afternoon you are there. There might be one every day, there might be one in Epcot and not in HS. I always go late August or September (going next week) and I always take either a poncho/rain coat or umbrella every day. It rains, I put on said rain gear or open said umbrella and go about my business, maybe jumping in a puddle if no one is in the splash zone. Wear clothing that drys quickly, take more than one pair of shoes so you can switch out the next day, enjoy being a kid again and playing in the rain. If you are going to F&W, I suggest a poncho or rain coat instead of umbrella, its hard as heck to hold that umbrella, a plate and eat at the same time. Also wear some sort of ball cap under your poncho hood, helps keep the rain off your face and holds the hood on better (I actually put my cap on outside my hood cause I own a lot of them and I'm just weird enough to do it).