This is full of the sadness of the termn of the seasons and how the dark hours cloak around the author. The optimism of summer has come to a sudden stop and the energy has gone as has the desire to fight the battle
The song is (for me) the epitome of something that is coming to an inevitable end. The summer metaphor seems to infer it's something that can't actually be prevented just as the end of a season can't be. Alongside it is the feeling it evokes & nothing will ever be the same again.