"a summer when" is a correct and usable part of a sentence in written English.
You could use it to indicate a particular summer or season, or to set the context for a story or event. For example: "It was a summer when I first realized the importance of hard work and dedication."
When all complaints about Lewis's rude, skittish, impossible social behavior are registered, there remained something good-hearted about him, as we can read in "First Job," Hersey's account of his pleasant summer with Lewis, a summer when Lewis was not drinking.
Long Island's newest electrical generator came on line last week, just in time to help LIPA squeak through a summer when power supplies may be pushed to the limit.
By Thomas Meehan The New Yorker, July 4 , 1970 P. 25Story about a 39 year old man & his memories of a summer when he was a college student & sold ice cream.
Looking back, that summer feels like the beginning of what would become the Black Lives Matter movement, a summer when my generation began to find the language we could use to fight racial injustice.
He recalled a summer when he was 15 and his parents sent him to Paris.
This doesn't happen to be a summer when we feel like being insulted.
"In a summer when everything else drowned, this ran wild on 28-foot vines".
John Quilter worked as a chef in Canada for a summer when he was 18.
Clark had joined the Ironworkers' Union during a summer when he worked at a steel fabrication plant.
In a summer when no one could agree on what constituted proper authority, more than statues might lose their heads.
It was a summer when a serial killer stalked young, brown-haired women with a.44-caliber pistol, a summer when a power failure plunged the city into darkness and looting.
