Summer rolls around again and Ari is looking forward to being out of school. He talks with his mom about taking on more hours at his job, but his mother reminds him that he doesn’t need to build a career right now, suggesting that he should relax more. Ari jokes that maybe he should fall in love instead; his mom comments that that might be a good idea. He goes out for a run with Legs and “happens” to cross by Dante’s old house; when he gets there, he finds that the Quintanas have returned, and he and Dante are reunited. They each realize that the other has changed physically, but they are just as close as they were the previous summer. Ari greets the Quintanas while Dante asks when he can take a ride in Ari’s truck.
Ari goes back home and returns with the truck around eight, but instead of going out themselves, Ari and Dante wait behind while Dante’s parents take the truck for a spin. While they’re away, Dante and Ari confront the elephant in the room: how Dante feels about Ari. They establish two rules: that Dante cannot kiss Ari, and that Ari cannot run away from Dante—including that if people start to talk about Dante being gay, Ari will have Dante’s back. Ari comments that he has a harder job, but Dante jokes back that he has to resist Ari, while all Ari has to do is be loyal to a wonderful person.
That night, they drive out to the desert. Dante shares that his mom has gotten pregnant, and says that he hopes it’s a boy, a boy that likes girls. They laugh but Dante confesses that he feels that he has to tell his parents, even though it will disappoint them. Ari asserts that his parents will love him no matter what, but Dante starts crying. Ari asks Dante again if he can’t tell how much his parents love him, but Dante insists he will disappoint them, just like he has disappointed Ari. Ari responds that Dante hasn’t disappointed him at all.
One night, Dante is working on a painting while Ari visits when Dante suggests that they kiss to see if they really don’t feel anything. Dante kisses Ari, and Ari kisses him back, but when Dante goes to deepen the kiss, Ari pulls back and says it didn’t work for him. They don’t talk for a few days afterward, but things soon settle down. At one point, Ari's mom goes to Tucson, leaving him alone with his dad, and Ari’s old resentment towards his father concerning the secrets his dad is keeping from him with regards to what happened in Vietnam and what happened to his brother resurfaces. He drives to Dante’s house and together they drive out to the desert, where Ari finally breaks down and cries.
Ari stops off at the drugstore where Dante works one day before work, and Dante tells him that Gina and Susie came in and asked about Ari as well as the accident. Ari is angry that Dante shared details, given that they had agreed not to talk about the accident, but Dante asserts that it’s fine because of how he was asked directly. Gina and Susie are shocked to learn that Ari was telling the truth the whole time, and Gina observes that Ari must really not want them to learn about Dante. That night, their dads go bowling as they drive out into the desert, where Dante reveals that there’s a boy named Daniel that he likes. Dante brings a couple of joints, so they go outside and get high while the sky begins to smell of rain. Eventually, the rain comes and they’re forced to run back to the truck. But Dante says they should go out in the rain anyway, so they strip down to nothing but their tennis shoes, and dance in it.
The next morning, Ari’s dad wakes him up to tell him that they have to drive to Tucson because the aunt his mother is visiting had a serious stroke and won’t make it. They leave Legs with Dante and his parents, as well as their house key so that Dante can water the plants. Ari drives him and his dad up and they don’t talk much while Ari thinks about everything from Dante to his dad to Aunt Ophelia. Ari lets his dad know that he was thinking about his aunt, and his dad reveals that Ari spent around nine months with his Aunt Ophelia when he was little, around the time of his brother’s trial, because his mother had a breakdown from the stress.
His aunt has passed away by the time they arrive. At her funeral, Ari notices that he and his immediate family are the only ones from Ophelia’s family there, despite the fact that it was clear that she was loved. When he asks his mom about it, she reveals that Ophelia was in love with a woman named Franny and was effectively divorced from the family because of it, but emphasizes that this did not matter to her or Ari’s dad. Ari is named in her will as the heir of her house, and his mom gives him the letters that she used to write to her. On their way back to El Paso, they get caught in a storm, and as Ari sits in the back of the car, he thinks that, unlike the other boys, he belongs to the rain.
Things are very different this summer, but in most ways, Ari and Dante have stayed the same. Ari is still hesitant to be openly affectionate towards Dante, but reveals that affection in his practices, like "accidentally" dropping by his house. Although to the reader it seems like it hasn't been that long since they met, the fact that Ari and Dante recognize significant physical differences in each other reminds us that Dante was gone for an entire school year. Their relationship, even with the relatively sparse communication, proves to be longlasting, as the boys resume like nothing ever happen.
Dante loving Ari, however, does make things different. Notably, Ari's issue is still not that Dante isn't gay, but when Dante brings it up, Ari draws a hard line with the no-kissing rule. But Dante's rule speaks to his worry that Ari won't be able to handle being his friend, even if he shrugs it off. Their drive to the desert reveals that Dante is also not as comfortable with his sexuality as one might assume. In wanting a younger brother who likes girls, Dante wants to make up for not being straight, for (supposedly) being a disappointment to his parents, and to Ari.
When Dante kisses Ari, even though it's with Ari's permission, it upsets Ari because he feels a rule has been violated, but also because it makes Ari feel conflicted. He doesn't vocalize this conflict directly, but his anger with Dante despite the fact that they agreed to try it out suggests that it's something that Ari really struggles to work through. In response, Ari breaks the rule Dante set for him and runs from him for a couple of days. But as seen through his reaction to his dad's secrets, when things are going well, Dante is the person he runs to.
The vulnerability that Ari shares with Dante drives him to keep everything about Dante private. For Ari, "Ari and Dante" are a two-man show where other actors are not welcome. Having Gina and Susie meet Dante feels like an invasion of privacy—like someone read his journal. His lack of response to Daniel also hints at his unwillingness to really share Dante with others. Dante is the only person Ari can be completely himself with: he trusts him enough to be literally naked in front of him save for his tennis shoes, an image that is a reversal of how Dante repeatedly refuses to wear shoes.
As it has for the whole book, the rain marks another transition, and this time, it's the passing of Ari's aunt. Here, the reader gets their first concrete sense of the dynamics of Ari's extended family through Aunt Ophelia. Ophelia's death is the catalyst for Ari's parents to begin being more open with regards to difficult things that happened with other members of the family, from sharing that his mother had a breakdown to revealing that Ophelia was lesbian. We also learn that Ari's parents—in stark contrast to the rest of their family—struck by Aunt Ophelia despite her sexual orientation. Ophelia is likely Ari's first introduction to an adult in his life who was gay. Not coincidentally, it's on the way back from this trip and upon receiving Ophelia's letter that Ari begins to think that he "belongs to the rain." Although he struggles to pinpoint it exactly, Ari has a strong sense that there is something that sets him fundamentally apart from most boys—something that he thinks about because of Aunt Ophelia's story.