Play in the extreme heat

This summer has been excruciatingly hot. It is miserable outside. I can't take my son to any of the parks because even with water play, he gets too hot just getting to the park. The other weekend, because it was so hot, my husband and I decided to go to an indoor play area for my son. He had a blast, but honestly, the temperature of the indoor play place wasn't much cooler than outside. We still let him have as much fun as he could but had to call it quits early because I was worried he would hurt himself in the heat. He was drenched in sweat as if he had jumped into a swimming pool. Next time we might just go to the pool instead.

Anyone else find it hard to play in summer? Where do you go to have fun?