We have gone in June, July and August. The 3rd week of June didnt seem to be too bad, in July we had to deal with some of the tour groups and after the 2nd week of august its shorter park hours. We only saw one family in storm along bay during the day. This august there was definetely much more rain than we cared to deal with and had to alter some of our swimming plans etc. If you are staying on site take advantage of ee in the parks for cooler touring, a mid afternoon nap and swim break and also make any ps you want. Many times we heard, sorry no walk ins accepted. This was aug. and I smiled as we were sitting with family enjoying our meals. etc. Also hydration is a big issues. Besides our refillable mugs at the resort, I always bring gatorade and koolaid into the park which we bring in the backpack. Also if we have a lunch buffet, I make sure to ask for an extra round of drinks before we leave and transfer that into our park backpack drink container. A mister fan is a definete must too. By 3 the heat really starts to get to you. If you can only spend one day in a park, then take lots of ac breaks etc.