I've been reminiscing about when and what would constitute the heart of summer. I have an idea that one specific time of summer could be considered the heart that every thing before leads to and every thing after leads away from. Sometime after school is out and before harvest and school starts up again.
I've played with the notion that it's the 4th of July. The anticipation of fireworks, picnics and the long summer nights. I can't put my finger on it. There are lots of events and activities that make summer special. Baseball (major league down to pee wee) could be part of it, it might be when time starts to slow down when you are 10 or 11 years old and you look forward to long days swimming, biking, reading and playing.
I looked forward to going to the library when I was that age...not so sure that would commonly be considered a great summertime activity for 10 year olds - but in a small Montana town without TV (very fuzzy in the summer), FM radio, or a movie theater - and before I could drive or work - the library was pretty appealing to me.
I got to know our old library and the old librarians quite well in the summer. The library was in the county courthouse. You entered a big lobby with a cool clickity marble floor when you came in the front door. More likely than not - no one would be in the lobby and it would be very quiet (same for the library which would generally be empty except for the librarian). I looked forward to finding anything that looked interesting and having lots of time to read it. I had as much time as I wanted to browse the stacks and maybe get a few hints from the librarians.
So maybe that's it - the heart of summer is when time starts to slow down. When you find yourself with a a big expanse of nothing, and consequently everything you want, to do.
May you find enough time to have nothing to do this summer.