Today, he went down his favorite slide and afterwards he told me it was "hot." It was kinda hot from the sun but it's plastic, not metal so it won't burn him. Besides, he's wearing sweatpants, so no worries!
I agreed with him and told him he was right, the slide was hot.
He then proceeded to blow on the slide - just the way I blow on his food when it's hot. Funny kid! I guess that's one way to solve the problem.