There are definitely songs that make us think of summer. And the second half of the 20th century brought us a lot of them. There are a quite a few lists that tell us the favourites. I picked out these:
(Sittin’ on the) Dock of the Bay by Otis Redding
Under the Boardwalk by the Drifters
Summer in the City by the Lovin’ Spoonful
Summertime by Ella Fitzgerald and Louis Armstrong
California Girls by the The Beach Boys
The Summer Wind by Wayne Newton
There are more, lots more. Every genre has them. There are classical music summertime songs. They all seem to have "summer" in the name, like Vivaldi's Summer. Summer is the great season. It deserves all this musical attention.
It makes me realize that with the rise of radio, popular and jazz music has come to define a society's experience of summer, not just a person's. That "collective unconscious" has been growing. Do we know what that signifies? Not me. It seems a mystery.