We were there from Memorial day until June 2. It was hot, very hot. We live in south carolina so we're used to the heat and the humidity to some extent. If the crowds had been smaller, it would have been better. I think the crowds were up due to Memorial Day though. We did find that it cooled down enough in the evenings though. It did rain two days on and off but we managed to not get caught in the rain somehow. One day, it probably rained 6 times, and we lucked out every time. We did take ponchos with us but never used them for people - just used one to keep the stroller dry. Gay Day/ Days was going on but I really don't think that effected the crowd level. Their Magic Kingdom day was on the weekend, and we planned to avoid MK on the weekend anyways.
October here in SC can be quite hot, but June is definately hotter. Plus the humidity starts to lift in Oct, but it's in full swing in June.
*I've gone three times the week after Christmas. I didn't have kids then and DH and I found it quite easy to do and see everything we wanted and then some. We didn't use a guide or touring plan, just common sense and fast feet! However, I wouldn't attempt that week with kids. June won't be as crowded as that Dec week - but that June trip was the first we attempted with young kids making us realize how much crowds effect us now.