The season traditionally dreaded by fa/tg/uys. Natural light for long periods, excessive heat and parents shouting at them to get out of the damn basement all combine to make overweight nerds suffer. In more recent years, /tg/ has been unable to get shit done because of newfags shitting up the place. During summer the levels of underage & increase dramatically (with the associated rise in tripfaggotry), causing an unavoidable decline in overall board quality until the little fuckers go back to school.
Some debate whether or not these "summerfags" are actually real, or just a new way to complain about or rationalize season-specific shitposts. According to moot, site traffic barely increases during the season; yet, considering his track record and common logic, he could be lying. Mentioning summer can occasionally lead people into debates over its existence, but in any case: idiots are always posting somewhere on 4chan, and there may or may not be more idiots in summer. In any case, it gives people a reason to be angry and blame something on someone, which is always fun.