The song was released by Source Music on July 19, 2018 as the EP title track.
[1] It was described by Billboard's Tamar Herman, as a "bright synth-pop track overflowing with rollicking brass and funky percussion".
[2] The song debuted at number 23 on the Gaon Digital Chart, on the week of July 21, 2018.
[5] "Sunny Summer" also debuted at number 25 on the Kpop Hot 100 for the week of July 22, 2018.
It also shows segments of hand-waving choreography with clips of the group spending their summer having fun together.