I challenge your hazy memory with a "false." Late spring was when we started seeing infections. Summer being hot was what we were told would help. The data showed otherwise. As you've provided none of your own, I'll go ahead and do the same.
There's a few states where the drop in the summer was really obvious, like Illinois and New York, and others that didn't spike until the fall, like Washington and Montana. Cases being low in the summer is common in the northern states, which is probably what GP is hazily remembering.
It spreads in the summer. Look at my plots (link above) for Texas’s summer surge. Was happening when I was a Boy Scout summer camp. Kind of weird to be in that communal environment at that time (albeit outdoors mainly, where spread is unusual).
