summer song i think only
fairyland
blue bird
glitter
july 1st
INSPIRE
independent

^these are the obvious ones since they were marked as that... but a lot of the sonsg people mentioned here give this certain feeling they give only in summer...

+ summer songs don´t mean just happy songs

Otsuka Ais Kingyo Hanabi is one of my favoruite summer sonsg but it is very sad....just like Ayus two hanabis....

I think a good summer remix is Endless Sorrow (Nicely Nice Skyblue Remix)