What you heard is generally true. It's also still pretty hot. The end of Aug starts to cool off, and is generally not as hot as the beginning of July, but don't expect it to be cool unless you get lucky and have a little cool spell when you are there.
That happened for us our last trip, and it was 85-90 highs during most of the trip. Good luck.
It does get a bit cooler at night, however, and it's still moderately crowded. So I advise that you go early and late to the parks, and take a break mid day and swim or hide inside somewhere.