The lyrics were inspired by producer and Danielle's partner Ariel Rechtshaid 's cancer diagnosis during the making of their second album, Something to Tell You; Danielle said that during the band's time off from touring, she wanted to be Rechtshaid's "hope when he was feeling hopeless" and a "light that shined on him when he was feeling very dark", which led to her singing "I'm your summer girl" over the demo's bass line.

It is clear from the onset that its addressee, i.e. Haim’s romantic interest, is in a vulnerable state. And as a result they are here to serve as his “summer girl”, which is a personification of their affection for and commitment to this individual.

The meaning of the song 'Summer Girl ', based on the lyrics What is Summer Girl about? The protagonist is thinking about a person she loves who is far away. She sees him in her mind when she closes her eyes, but he seems unreachable. She considers herself his "summer girl" and wants him to understand that she loves him unconditionally.