"Cruel Summer" is a synth-pop, industrial pop, and electropop song composed of synths, wobbling beats, and vocoder-manipulated vocals.

Initial reviews of Lover praised "Cruel Summer" for its melodic composition and catchy sound, specifically highlighting the hook and bridge.

[11][12] It has a "ranting" bridge underscored by skittering synths,[13][14][15][16] distorted vocals[5] manipulated by a vocoder,[17] and a hook that consists of a long, high, fluctuating "ooooh".

[13] Billboard's Heran Mamo opined that the song's lyrics see Swift "wrestling with strong feelings", where they paint "the picture of an emotional night out".

[22] Anna Gaca, writing for Pitchfork, called the song a "drama-free delight" with "magnetic pink glow".

[28] The track originally charted as an album cut within the top 30 in Singapore (8),[29] Malaysia (13),[30] Ireland (20),[31] New Zealand (20),[32] Australia (23),[33] the United Kingdom (27),[34] and Canada (28).

[35] In the United States, the song debuted at number 29 on the Billboard Hot 100 dated September 7, 2019; it is one of the seven tracks from Lover to reach the top 40[36] and remained on the chart for two weeks.

[45][47] "Cruel Summer" became Swift's record-extending 41st song to reach the top 10 on the Billboard Hot 100 and the fourth Lover track to do so.

[52][53] On US Billboard airplay charts in 2023, "Cruel Summer" became Swift's eighth number-one single on Radio Songs, where it reigned for 12 non-consecutive weeks surpassing "Blank Space" as her longest running number one.

[53][57] Jason Lipshutz of Billboard commented that the single's resurgent success "simply demonstrates Swift's current ubiquity, unprecedented in the modern music era".

[58] In January 2024, the song topped the Adult Contemporary chart, marking Swift's ninth number-one single.

[60] Elsewhere, "Cruel Summer" reached new peaks in Australia (1),[61] Canada (1),[62] Singapore (1),[63] New Zealand (3),[64] Ireland (4),[65] Malaysia (6),[66] and Brazil (54) as well.

[79] St. Vincent described the resurgent success of "Cruel Summer" as "crazy": "I mean, I always thought in the context of that record, like, 'That should be a single, it’s a great song.'

Jon Caramanica of The New York Times commended the "thick, ethereal" production and Swift's signature vocal motifs such as the "question-mark syllables" and the "hard-felt smears".

[81] Mikael Wood of the Los Angeles Times proclaimed "Cruel Summer" to be the best song of Lover and said the bridge where Swift "shrieks about the devil might be the punkest thing you'll hear all year".

[84] Natalia Barr, writing for Consequence, highlighted Swift's vocal delivery in the song's bridge ("He looks up, grinning like a devil"), calling it "simultaneously funny, agonizing, and thrilling, and needs to be created into a viral YouTube loop immediately".

[93] Brittany Spanos of Rolling Stone wrote in 2023, "Swift flaunts a rock-star edge alongside a grand sense of romantic urgency" in "Cruel Summer", making it one of her best songs.