Approximately 30 Days of Summer, an ongoing series
The appeal of summer, from the music lover's perspective, is that it allows for infinite variety. If music serves as something other than pleasant background to the day's tasks, then it's clear that certain songs, albums, artists, are appropriate at some moments and not at others. A sunny day is a terrible time to listen to The Smiths; Whiskeytown isn't quite right when it's snowing. The summer is, by contrast, a time to do all the things one normally doesn't do: listen to the big and obvious songs you love, engage in all forms of nostalgia, add in longer and more complicated songs, slower songs, rub all manner of genres right up next to each other.
Most hallowed is the song about summer, of which "A Summer Wasting" is my favorite, capturing, as it does, the precise feeling of accidentally-intentionally doing absolutely nothing over the summer.