The first day of September is markedly cooler than any day in August. As if fall arrived on command. There's a poem I always think of when the summer is ending. I posted it last year, so I'll just post a line or two (or five) here.
this high summer we love will pour its light
the fields grown rich and ragged in one strong moment
then before we're ready will crash into autumn
with a violence we can't accept
a bounty we can't forgive