Lovin' Spoonful, Summer in the City, 1966
Chad and Jeremy, A Summer Song, 1964
Mungo Jerry, In the Summertime, 1970.
Robin Ward, Wonderful Summer, 1963
Seals and Croft, Summer Breeze, 1972
Johnny Rivers, Summer Rain, 1967. It came out the summer we were all listening to the Beatles' Sargeant Pepper's Lonely Hearts' Club Band, and captures the mood of that summer for me.
Eddie Cochran, Summertime Blues, 1958. An early teenage anthem in rockabilly style by one who died young. Wikipedia:
On Saturday, April 16, 1960, at about 11.50 p.m., while on tour in the United Kingdom, 21-year-old Cochran died as a result of a traffic accident in a taxi (a Ford Consul, not, as widely reported, a London hackney carriage) traveling through Chippenham, Wiltshire, on the A4. The speeding taxi blew a tire, lost control, and crashed into a lamp post on Rowden Hill, where a plaque now marks the spot. No other car was involved.[11] Cochran, who was seated in the centre of the back seat, threw himself over his fiancée Sharon Sheeley, to shield her, and was thrown out of the car when the door flew open. He was taken to St. Martin's Hospital, Bath, where he died at 4:10 p.m. the following day of severe head injuries.[12] Cochran's body was flown home and his remains were buried on April 25, 1960, at Forest Lawn Memorial Park in Cypress, California.
Blue Cheer, Summertime Blues, 1968. A heavy metal version of the Eddie Cochran rockabilly number. The first heavy metal song? If you remember Blue Cheer, I'll buy you a beer.
Doors, Summer's Almost Gone, 1968
Sarah Vaughn, Summertime, early '50s
Jamies, Summertime, Summertime, 1958
Percy Faith, Theme from a Summer Place, 1960. I remember a girl complaining that this "old fogey music" was being played on the R & R station we were listening to: had to have been either KRLA, KFWB, or KHJ, Los Angeles.