Last Whiff of Summer is the two-part Season 4 premiere episode.
Frankie tries to make summer great again for her family, but once Mike lets it slip that Axl is his favorite, Frankie's plans for the summer are thwarted. Axl is forced to attend summer school to re-take his English class. Brick attends to his summer tomato project while Sue does her best to engage Mike so she can proceed with her scrapbook.
The episode begins with Frankie and Mike arriving at the Heck house with a carload of summer supplies, and Mike notices "the smelly thing in the car". Frankie points out to him that it is fresh-cut grass that he is smelling, and the two reminisce about their summers as children. Frankie talks about that "feeling of summer that you can't describe. This." meaning summer fun, peace and relaxation. She plans to have an amazing summer as they walk into the Heck house, to see Axl, Sue and Brick on their electronics, zoned out, much to Mike and Frankie's dismay. Frankie realizes that Axl will be a senior in high school the following year, and it may be their last summer together as a family. Mike shoos them from various electronics around the house, forcing them to do summer activities that they do not like. Meanwhile, Brick finds a sick tomato plant in his backpack, apparently from when his class studied photosynthesis, and plants it in the yard. Later, the parents come out of the house and force the kids to go to a drive-in movie with them. As they get to the movie, they fight in the car, resulting in Mike removing them from the car and forcing them to go to the nearby playground so they can have some alone time. At the playground, Axl, Sue and Brick argue about if the parents have favorite kids. Axl agrees, Sue denies it and Brick sides with Axl. They return to the car and Sue asks Frankie if she and Mike have favorite kids. Frankie denies this, but Mike states out of the blue that he likes Axl the most. Sue angrily leaves the car and retreats to the playground to cry.
A few days after the drive in, Frankie finds a report card under Axl's bed and is infuriated by the fact that Axl has failed his previous year's English course. Axl is forced to go to summer school. Meanwhile, Sue ignores her father and Brick's tomato plant gets better and grows rapidly. As Axl is failing to study his summer-school English course, Mike gives him negative attention and Sue none at all, while she is making a scrapbook called "The Summer of Sue and Dad" to win Mike over. She realizes that if she wants to get attention, she has to misbehave and be defiant. She misbehaves and Mike does not pay any attention to her, much to Sue's frustration. Fourth of July rolls around and Frankie gathers the family to go to a local park to watch the fireworks. The kids let it slip that Mike is their favorite parent which angers and shocks Frankie. She yells at them, and then the fireworks start in the distance. Frankie realizes she drove to the wrong location and warns the family to not say anything.
August comes around, and Bricks tomato grows, resulting in him having to give it support, by using Frankie's tampons, then Sue's bra, then a pair of underpants that he found at the park, which disgusts Frankie. She asks Brick if there is anything else he would like to do, and he replies by telling her he would like to enter his giant tomato in the River County Fair, which is three hours away from Orson, and Frankie reluctantly agrees. Axl drives Brick, Frankie and the tomato to the fair, whilst Sue rides with Mike, wanting to be disciplined. Upon arrival at the fair, Brick states he does not feel well and Frankie takes Brick out to give him some fresh air. She orders Axl to meet them at the funnel cake stand, and Axl ignores her as usual. He mistakenly drives his car into a destruction derby, resulting in the car being destroyed and the tomato squished by another car. The family is angered and Axl remembers he left his English essay in the car which is being hauled away to the dump. The family minus Sue races after the car, and Sue tries to get lost, only to get scolded by Frankie. The family is depressed, and they leave. An argument in the parking lot is interrupted by a show of fireworks. On the drive home, Frankie narrates that a great summer cannot be forced. In the credits, a montage of Sue's scrapbook is displayed, showing the summer's activities.