Why Don’t We close their 2019 project – in which they release a single each month – with “Chills.” In the track the five-piece sing about the way their love interest simultaneously warms their heart and gives them chills. A similar theme appears in their February 2019 single, “Cold In LA” which discusses the chilly aftermath of a romantic partner leaving.

The track was first revealed on December 24, 2019 when Warner Music Spain posted an image of Why Don’t We to Instagram. The caption displayed: “#CHILLS @whydontwemusic 🥶30/12.” The post was later deleted by Warner Music after what appeared to be a promotional mishap.

On December 28, the band posted a snippet of the track to Instagram revealing its title and release date.