The lyrics differ from most songs about the summer by lamenting the heat, contrasting the unpleasant warmth and noise of the daytime with the relief offered by the cool night, which allows for the nightlife to begin.

The recording is an early instance in pop music of added sound effects, made up of car horns and a pneumatic drill to mimic city noises.

In need of new material for their next LP, John Sebastian, the band's principal songwriter, recalled a song composed and informally taped by his teenage brother, Mark,[7] titled "It's a Different World".

[8] While recording the song, the band determined that a bridge or middle eight was needed to complement John's "tense" and "free-swinging" parts, prompting bassist Steve Boone to suggest a "jazzy figure", a "piano interlude" which he later said "sounded a little bit like [American pianist] George Gershwin".

[14] The combined unpleasantness of the daytime heat and noise are directly contrasted with the relief offered by nighttime, whose cooler temperatures allow for city nightlife to begin, consisting in dancing and finding dates.

[15] In contrast to the verse, the next section, which Everett writes "ought to be called the bridge", is a major mode, suggestive of the "different world" of the night described in the lyrics.

[20] John struggled to play the Wurlitzer electric piano part, prompting the arranger Artie Schroeck to step in as a session musician.

[17] After hearing the initial playback, Yanovsky complained that the song's percussion was not loud enough, expressing to Halee: "I want the drums to sound like garbage cans being thrown down a steel staircase.

[33] It held the position for three weeks, becoming what author Jon Savage terms the "American song of the summer",[30] before losing the top spot to Donovan's "Sunshine Superman".

[17] While the band's next single, "Rain on the Roof", reached number ten on the Billboard Hot 100,[46] both Butler and Boone felt it was a mistake to release the song as the follow-up to "Summer in the City".

[17][note 4] Among contemporary reviews, Cash Box magazine predicted a "sure-fire blockbuster", describing the song's "repeating hard-driving riff" as "contagious".

[49] Record World's review panel selected the song as one of their three "single picks of the week", describing it as "[w]ild, experimental, hypnotic, terrific, positive in approach and a powerhouse release".

[50] In the UK, Melody Maker's reviewer wrote that the song displayed the musical diversity of the Lovin' Spoonful, given its divergence in style from their earlier 1966 single, "Daydream", and predicted its inclusion on Hums of the Lovin' Spoonful would boost album sales in both the U.S. and the U.K.[51] In Billboard, Johnny Borders, the program director of KLIF in Dallas, reported that while the radio station's early summer rotation had been based around oldies due to the poor quality of new music, the release of "Summer in the City" improved the situation.

[52] David Dachs' 1968 book, Inside Pop, discusses the song in the context of the Lovin' Spoonful's diverse styles, while also writing its lyrics display "a hip and jazzy swing".

[53] In a retrospective assessment, author Ian MacDonald categorizes "Summer in the City" as a "cutting-edge pop [record]"[54] and one of many "futuristic singles" to appear in 1966, such as the Beach Boys' "Good Vibrations", the Byrds' "Eight Miles High" and the Four Tops' "Reach Out I'll Be There", among others.

[55] He describes it as representative of a time period when recorded songs began to employ sounds and effects difficult or impossible to recreate during a live performance; when the Lovin' Spoonful played the song in concert, John was unable to both sing and play the piano part simultaneously, requiring Butler to perform the lead vocal.

[56] Richie Unterberger similarly writes that it proved the band's ability to extend beyond "sunshine and light",[57] praising its major-minor shifts and describing the sound effects as "particularly inventive" while "mercifully" not being overdone.

[3] Musician Chris Stamey describes the song as a "fantastic, cinematic record" and highlights the same features as Unterberger, particularly the major-minor changes which help emphasize the two different musical moods.

[58] In The New Rolling Stone Album Guide, Paul Evans also commends the sound effects and key signature changes, writing the latter retains both "a sense of wonder and deliberate naiveté".

[61] Authors Keith and Kent Zimmerman call it "a twentieth-century pop classic", comparing it to Gershwin's An American in Paris and Richard Rodgers' Slaughter on Tenth Avenue.

[67] The American indie band Eels recorded a cover that appeared on the deluxe edition of their 2013 album, Wonderful, Glorious, later described by Boone as "spooky and cool dirge-like".

[70] Jones' version has been sampled by numerous hip hop artists,[17][35] including on the Pharcyde's 1992 song "Passin' Me By",[71] which incorporates the organ intro.