This may be stretching the boundaries of "summer song" a bit, but bear with me.
I tend to become a bit obsessive about songs. If a song moves me, I'll listen to it over and over again, to the point of annoyance for anyone who has the misfortune of being in my vicinity. This is one of those songs - it's not new, but I didn't discover it until the local radio station I listen to recently put it in heavy rotation. Now I sit there in the car just hoping it will come on, so I can turn the radio up and just let it wash over me.
This is a live performance, a strong one, of the song.
So it may not have been released in the summer, but as far as I'm concerned, it's a summer song - summer of 2013.
"You Will Leave a Mark," A Silent Film.