Summer time Blues by Blue Cheer !
What's one song that best represents summer time?
Probably Mungo Jerry "In the Summertime".
"Summer Song" by Chad Stewart and Jeremy Clyde is in there somewhere too. (It's a bit sickly sweet but quite evocative of summer).
I don't know about "The best" definition. But I can only give what I listened to & have in mind right now...
Cascada - Summer of love
DJ Jazzy Jeff and the Fresh Prince - "Summertime"
This song is an oldie, but it just takes me back to being a kid in the summer. It is "Summer" by War.
Saturday in the park by Chcaigo.
Just about any of the "up tempo" songs by The Beach Boys or Jan & Dean.
Boys of summer