Hi! We went from June 6-9 last year and the crwods were minimal. It was pretty warm, I did get quite sunburned even with sunscreen on! I think our longest wait was Mr. Toad and that was about 10 minutes. And alot of the lines are in the shade so it wasn't too bad. I do remember standing in direct sun for the parade though and I was really sweating by the time it was over.
Have fun, we will be there again June 8-12. From what I have heard, the crowds start gathering around the middle of June when most schools get out so you may run into some longer lines than we did. But with fastpass is is definitely manageable.
Andrea