Perhaps it focuses on the changes in Harry's relationships. He might grow closer to some friends while drifting apart from others. For example, his bond with Hermione could strengthen as they explore some new magical mystery together during that summer. And his relationship with the Dursleys could also take a turn, like they finally start to show a bit of understanding towards him.
Well, it could be about how the wizarding world is adapting to new magical discoveries. Maybe new spells are found that change the way magic is taught at Hogwarts.
In a 'Harry Potter Summer Training' fanfiction, perhaps the training is organized by some of the older students who have graduated but still want to help. They could be teaching the younger students advanced dueling techniques. Harry might discover a new aspect of his magic during this training, something that has been dormant until now. For example, he could have an affinity for a type of magic that is rare, like time - related magic. The story could then revolve around him exploring this new power under the guidance of the older students.
Well, without actually reading the fanfic in full, it could potentially involve Harry Potter experiencing personal growth during the summer. Maybe he discovers new magical abilities or forms deeper friendships. It might also include changes in his relationship with the wizarding world, like getting involved in new secrets or plots.
He could work at Weasleys' Wizard Wheezes. He has a good relationship with the Weasley family, and it would be a fun place for him to work, helping with inventing and selling all kinds of magical pranks and toys.
It could also focus on some of the minor characters from the original series. For example, Neville could be a main character in this fanfic and his growth and change during the summer could be the main focus. Or Luna, with her unique perspective, could be in the center of all the happenings during that summer of change.
In some fanfictions, Harry might change physically. He could have grown taller or more muscular from any summer training he did. For example, if he was secretly practicing Quidditch on his own, it could have affected his physique. Also, mentally he could have become more mature. Maybe he spent the summer reading advanced magic books and this broadened his understanding of magic, making him more confident and less impulsive in his actions.
Well, physically he could change too. Fanfic writers might describe him as growing taller or stronger during the summer break. Emotionally, he might deal with his past traumas better. For example, if he had nightmares about Voldemort, he could learn to overcome them, perhaps through some new magical techniques he discovers or with the help of his friends. This could make him more resilient and less haunted by his past, which is a significant change for his character.
Harry Potter himself is surely important. He is the main character and the one going through the 'summer of change'.
It could center around the changes that occur in the wizarding world during a particular summer. For instance, new spells could be introduced, or there could be a shift in the relationships between different magical families. It might also be about how the Hogwarts students adapt to these changes when they return to school after the summer.
The twin could change the plot by being more interested in academic magic than Harry. This might lead to him uncovering secrets in the library that Harry misses, which could be crucial in the fight against Voldemort.