Yes, if swimming is important, go in August. We have gone 3 times over the past two summers, once in June, once in late July/early August, and once in mid-August. It is hot, but totally doable. I prefer the hot weather over the more unpredictable winter weather. You don't know if you need shorts and t-shirts or jeans and sweatshirts in the winter so you have to take it all. Summer is so easy! Love it.
If swimming doesn't matter and you don't like heat, or especially heat & crowds together, then go in January.