This one comes from a story called, "My Pretty Pony". To put this in the proper context, Clive, a boy of about 8 or 9 years old, is talking to his grandfather for the last time (of course, neither of them know this yet). His grandfather had seen him get beat at a game of hide-and-seek, but only because the other boy cheated by counting too fast. This provides a great backdrop for the story because grandpa's instruction to his grandson, Clive, is all about how time goes very slowly as a child, speeds up a bit in the middle years, then seems to take on a mind of its own after a man hits about 45 or so.
In this part of the conversation, early on, Clive's grandpa is asking Clive if he can imagine what summer is like, how he feels about it, etc. as it will be important for him to relate to Grandpa's more recent experiences of summer later in the conversation. Here's how Stephen King narrates summer for Clive at his young age:
Those days. All those days, stretching away across the plains of June and July and over the unimaginable horizon of August. So many days, so many dawns, so many noon lunches of bologna sandwiches with mustard and raw chopped onion and giant glasses of milk while his mom sat silently in the living room with her bottomless glass of wine, watching the soap operas on the TV; so many depthless afternoons when sweat grew in the short hedge of your crewcut and then ran down your cheeks, afternoons when the moment you noticed that your blob of a shadow had grown a boy always came as a surprise, so many endless twilights with the sweat cooling away to nothing but a smell like aftershave on your cheeks and forearms while you played tag or red rover or capture the flag; sounds of bike chains, slots clicking neatly into oiled cogs, smells of honeysuckle and cooling asphalt and green leaves and cut grass, sounds of the slap of baseball cards being laid out on some kid’s front walk, solemn and portentous trades which changed the faces of both leagues, councils that went on in the slow shady axial tilt of a July evening until the call of “Cliiiive! Sup-per!” put an end to that business; and that call was always as expected and yet as shocking as the noon blob that had, by three or so, become a black boy-shape running in the street beside him – and that boy stapled to his heels had actually become a man by five or so, albeit an extraordinarily skinny one; velvet evenings of television, the occasional rattle of pages as his father read one book after another (he never tired of them; words, words, words, his Dad never tired of them, and Clive had meant once to ask him how that could be but lost his nerve), his mother getting up once in a while and going into the kitchen, followed only by his sister’s worried, angry eyes and his own simply curious ones; the soft clink as Mom replenished the glass which was never empty after eleven in the morning or so (and their father never looking up from his book, although Clive had an idea he heard it all and knew it all, although Patty had called him a stupid liar and had given him a Peter-Pinch that hurt all day long the one time he had dared to tell her that); the sound of mosquitoes whining against the screens, always so much louder, it seemed, after the sun had gone down; the decree of bedtime, so unfair and unavoidable, all arguments lost before they were begun; his father’s brusque kiss, smelling of tobacco, his mother’s softer, both sugary and sour with the smell of wine; the sound of his sister telling Mom she ought to go to bed after Dad had gone down to the corner tavern to drink a couple of beers and watch the wrestling matches on the television over the bar; his Mom telling Patty to mind her own p’s and q’s, a conversational pattern that was upsetting in its content but somehow soothing in its predictability; fireflies gleaming in the gloom; a car horn, distant, as he drifted into sleep’s long, dark channel; then the next day, which seemed the same but wasn’t, not quite. Summer. That was summer. And it did not just seem long, it was long.