Lovato co-wrote "Cool for the Summer" with Alexander Erik Kronlund, Savan Kotecha, and its producers Max Martin and Ali Payami.

To promote the song, Lovato performed it at pool parties a few days after its release, and on several television programs such as The Voice Australia, Sunrise, the 2015 MTV Video Music Awards and Jimmy Kimmel Live.

Demi Lovato co-wrote "Cool for the Summer" with Alexander Erik Kronlund, Savan Kotecha, and its producers Ali Payami and Max Martin—who also handled programming.

[12] NME editor Nick Levine praised the song's style, describing it as a "massive EDM-tinged-tinged pop banger with lyrics hinting at an exploratory same-sex tryst".

[16] The track's ambient production consists of a melodic piano introduction,[12] which is followed by a buzzing synth beat[1][11][12][14][15] accompanied by guitar riffs in the chorus.

[1] Jason Lipshutz of Billboard gave the song a rating of four-and-a-half stars out of five, calling it Lovato's "most self-assured statement to date".

[12] Idolator gave it an average rating of 7.5 out of 10, writing, "from the hook-filled production to the tongue-in-cheek lyrics, it only takes one listen to know that 'Cool for the Summer' is going to be huge".

[11] Nolan Feeney of Time stated that "Lovato's sultry vocals and producer Max Martin's Midas touch melt the track's air-conditioned synths into a sweltering, rock-infused banger".

Club called the song an "unstoppable hit" and described it as "an icy rush of electro-pop seduction in praise of fleeting romance".

[21] In a review of the song's parent album Confident, Yu Tsai of USA Today praised the lyrics, writing; "Lovato has long-infused her brand of pop with rock 'n' roll grit, heard here and on the electric-guitar riffs of first single 'Cool For The Summer'.

While its limp attempts at being provocative emit little heat ... [the track] is still one of the catchier songs on the album, whose other potential radio hits are harder to identify.

Spin ranked the song at number 101; the magazine's editor Jia Tolentino wrote; "From that first icy, neon piano riff, 'Cool For the Summer' feels like a Miami drag race in an '80s dream, with a muscular force in Demi's chorus that makes those sweet, girlish verses seem like a lie you'd tell your parents just before you'd sneak out of the house".

[24] In Village Voice's 2015 "Pazz & Jop" mass critics' poll of the year's best music, "Cool for the Summer" was tied at number 29 with three other songs.

[25] Stereogum's Chris DeVille considered it the 23rd-best song of the year, writing that "the parade of undeniable hooks on 'Cool For The Summer' got Lovato's next chapter off on the right foot".

He also commented on the song's impact in Lovato career, describing it as "a breezy, dusky pop serenade, that ramps up with husky guitars before it ends.

In the United States, "Cool for the Summer" debuted at number 36 on the Billboard Hot 100 dated July 18, 2015, with opening sales of 80,000 copies.

The release of its lyric video on July 7, 2015, also prompted a gain of 185 percent in US streams to 2.4 million, the second-largest advance on the chart that week behind Fetty Wap's song "679".

[41] On September 23, 2016, "Cool for the Summer" was certified Double Platinum by the Recording Industry Association of America (RIAA), denoting sales and streams of two million copies in the US.

Rob Copsey from Official Charts described the video as "hot" and wrote that it "sees her hit the road with her gal pals (and a bottle of her own-brand hydrating mist) before getting it on with each other at a wild house party".

[64] Christina Garibaldi of MTV News deemed the video "seductive, sassy and smokin' hot", and noted it marked "a new chapter of her career, as she exudes a confidence and sexiness that we haven't seen before".

[74] Lovato also performed the song at the Major League Baseball All-Star Game in Cincinnati on July 11, replacing Ariana Grande.

Taylor Whatherby of Billboard magazine wrote, "Lovato nailed her vocals as the rest of the girls jammed on electric guitars, a keyboard, and drums".

[90][91] On December 31, 2015, as a headliner of Dick Clark's New Year's Rockin' Eve, she performed another medley of "Cool for the Summer" and "Confident" in Times Square, New York.

[98] During a show at the Staples Center in Los Angeles on August 20, 2015, singer Kelly Clarkson performed a downtempo version of the song, which was backed by an acoustic guitar and piano.

[102] "Cool for the Summer" was featured during a lip sync battle in the ninth season of RuPaul's Drag Race,[103] with Kesha as the special guest judge.

[104] Lindsay Harvey of Billboard wrote that the remix by Plastic Plates "slows things down a bit" and features a "steadily paced bass line" with "lighter rhythms".

In January 2022, Lovato held a "funeral" for her pop music ahead of the release of her eighth studio album Holy Fvck in August of that year.

[188] "Cool for the Summer (Rock Version)" was produced by Warren "Oak" Felder, Keith "Ten4" Sorrells, and Alex Nice, all of whom contributed to Holy Fvck.

[187] Hannah Dalley of Billboard described the snippet shared by Lovato to announce the rock version's release as consisting of "pounding drums and razor-edged electric guitar".

[186] Upon the full song's release, Starr Bowenbank wrote for the same publication that the rock version "swaps the original's poppy synths and uptempo instrumentation for a darker sound backed by electric guitars and grittier lyric delivery from Lovato".