The wife and I are booked for the second week in September. How are the crowds that time of year?
All the other posts are valid. I've been the last two years, two years ago was right after Memorial day, and last year was the week after that.
Crowd wise, you can easily get on rides at less then 20 minutes without a fast past for most rides, then you have your rides that will probably always require a fast pass, if you don't mind getting split up and doing single rider you can usually get on faster. The crowds do swell and go down. Last year there was one time on space mountain the fast pass line was 40 min and the walk on ride was 10. Go figure. But generally if all the rides are up and running there is usually one you will just be able to walk on. No fuss no muss. With the Food and Wine starting earlier it might add a few more people to Epcot and also same with Pandora, but until the
MNSSHP dates released we wont really know. I would still get your FP done in the morning and keep scheduling, but the walk ons shouldn't be that long.
The weather isn't that bad. Hot but not a melt the pavement hot, just enough to keep you in shorts and tee shirts and a nice small sheen of sweat, but not buckets. Just wear breathable clothes and you should be fine. The water rides will still be nice. Rain does happen but in the past two years have only seen it really pour one time. The pool is still busy and a nice break in the day. It could feel a little hot if your from north, but I'm in AZ so its a nice break, but the humidity does remind me of my younger days in Oregon. The humidity makes you feel the heat, but a nice breeze is a welcome thing.
Food lines are pretty good. Only one place we actually had to wait, and BOG still had reservations available. That should tell you something.