Musically, "Nuclear Seasons" is a slow-burning dark wave, synth-pop, electropop and lo-fi song with low-lying synths, industrial textures, and a shadowy atmosphere.

The song's 80's-influenced vocal melody has been described as the centerpiece of its "lavish, if busy, production", which features flourishes of synths rings, electronic buzzes, and pattering and crashing beats.

[6] Its lyrics speak of things such as burning cars and falling through the clouds, which according to Art Ivan of Tiny Mix Tapes, depicts what a rapture would look and sound like.

"[7] Charli specifically notes what she sees as a decay in youth culture, stating "I don't feel like there's anything for people to really grab onto these days.

"[7] While reviewing True Romance, Kevin Liedel of Slant Magazine called the song a "K-pop-esque opus" which showed one of only a few moments of genuine spontaneity.