Fitzgerald uses weather to reflect the characters and the plot. The physical heat of the weather forebodes the heated argument that kills Gatsby’s dream, destroys Wilson’s sanity, takes Myrtle’s life, and reunites Daisy and Tom.
Various scenes in the beginning of the chapter relate to the heat. Nick describes the day as “broiling,” and the conductor says it all, “Hot! Hot! Is it hot enough for you?” Everyone on the train is uncomfortably perspiring and miserable.
Fitzgerald uses this scene as a precursor to the coming misery. Tom is shocked when he realizes that Daisy has feelings for Gatsby, and “trembling with his effort at self-control,” declares that they’ll all go out. When they stop for gas, it’s clear that Wilson is ill. He has just discovered that Myrtle has a lover, and he’s locked her up to prevent her from running away. Nick remarks about the “relentless beating heat” and recognizes that Wilson and Tom are alike in that they both have discovered their wives love someone else. The extreme heat parallels their reactions of anger and illness.
As they argue about where to go, Nick thinks about the sweat that tortures his back and his underwear “climbing like a damp snake around my legs.” Both the heat and the events of the day make him uncomfortable. Even the hotel room they rent is “stifling,” and not even opening the windows helps to cool off its occupants.
But while the chapter begins with a plethora of references to the heat, Fitzgerald does not find it necessary now to mention it. Instead, he bombards the reader with one shocking revelation after another. Tom immediately confronts Gatsby about his past and about his intentions with Daisy, which upsets her. Tensions increase as Gatsby wants Daisy to disavow any love for Tom, which she cannot do. Once Tom reveals the truth about Gatsby’s past, he has no argument of defense, “so he gave that up and only the dead dream fought on.” The chapter continues with the hit and run, Wilson’s devastation, Tom and Daisy’s conspiring, and Gatsby’s ruin. The characters experience a range of negative emotions throughout.
The heat has served its purpose of foreboding the terrible events of the day and night, and echoing the characters’ frames of mind.