Having had a string of unseasonably cool or downright cold trips in November, December and March in the last few years, we decided this year to just skip the questions and go during the summer. It's easier to not have to take DS out of school, plus it solves the "what weather do I pack for?" question. We were just there in late June and honestly, at times I was questioning my decision! But we also swam EVERY DAY - and I grew up in the south, so I'm not one of those people who will swim if it's 60F outside...it has to be hot for me to want to get in the water! So enjoying the pool with my kiddo every day was a rare treat. And the long park hours and plethora of special summer events are a great trade-off for the heat!
Another thing - I'm not a napper at all, so the afternoon break has always been a tough thing for me. Being able to swim meant we had a break during the hottest part of the day and were able to cool our bodies down before showering and changing for the evening shift. We planned our breakfasts late (to take advantage of the "cooler" hours during EMH) and get out of the late morning sun. We also planned our dinners early for the same reason. We also do mostly signature restaurants for dinners, so those dinners were long enough that by the time we were done, the sun wasn't down, but it was low in the sky and less of a factor in how the temperature *feels*. (we tend to just eat 2 meals a day when it's that hot, with the occasional snack thrown in)
(Oh, we also went in May 2009 on Mother's Day week and it was as hot as it was this June - hotter than normal for that time, and the day we left was when the infamous month+ of rain began - it was above and beyond the typical afternoon thunderstorm pattern. I don't think I've ever read so many reports of day-long rain deluges!)