The sun is out, school is out, and songs displaying any degree of emotional complexity are out.
Take, for example, Stardust's Music Sounds Better With You - four minutes of French funk built upon a brutally efficient four-bar loop, that became the signature sound of summer 1998.
Big, brash pop songs also fit the bill, with Rihanna's Umbrella (2007) and Little Mix's Black Magic (2015) both benefitting from a summer boost.
NB: This rule doesn't just apply to songs. Summer blockbusters are the dumbest form of cinema; "beach reads" are inevitably schlock romances and thrillers; and summer TV is epitomised by Big Brother and Love Island.
Basically, we all become idiots in the heat.
2) It should make you feel like you're on holiday
The rise of affordable package holidays in the 1980s prompted an influx of European songs to the summertime charts. Holiday hits like Spagna's Call Me, Sabrina's Boys and Opus's Live Is Life were all smuggled into the Top 40 by British tourists.
Ever since, summer songs have fared better if they somehow feel "exotic", with the rhythms of Latin America and the Caribbean providing several seasonal smashes.
In the modern era, though, summer hits have tended to be euphoric pop - with the likes of Carly Rae Jepsen's Call Me Maybe, The Black Eyed Peas' I Gotta Feelingand Sonique's Feels So Good all providing a soundtrack to the sunshine.
5) It should be released before the summer
While it's possible for a late-breaking hit to elbow its way to the front of the pack, the song of the summer has usually been hanging around for a while before it takes over the world.
Drake's One Dance, which topped the charts for 15 weeks last year, was originally released in April.
More impressively, the reggae-tinged morality tale Rude, by Canadian band Magic!, had been hanging around for 11 months before it clawed its way to number one in August 2015.
6) But it should have the word "summer" in the title
It's a cynical tactic, but it works.
From Mungo Jerry's lyrically-questionable In The Summertime in 1970 to Demi Lovato's Cool For The Summer in 2015, releasing a song about the summer in the summer guarantees you a hit almost as quickly as putting the words "featuring Justin Bieber" on the sleeve.