Mia and her family live just a couple hours away from Chicago. She lets us in on that fact when she's dressed in a one-size-fits-all shepherd costume for the Christmas play at school:
My feet were freezing in the sandals that in my humble opinion no one should have to wear in northern Illinois in the middle of December. (Pro.2)
Brrrr… We agree, Mia. We agree.
Beyond freezing her toes off, the setting provides the backdrop for the story but doesn't matter much in the big scheme of things—we could just as easily see Mia growing up in any state. The fact that her family lives only a few hours outside of Chicago, where professor Jerry teaches, is just a bonus. But again, you could probably plop Mia down anywhere and she'd be similarly close to some sort of professional. It's not like Jerry's her neighbor or anything.
The generalness of the setting and the ordinariness of it, too, both contribute to our understanding of Mia as ultimately an ordinary kid. Yes, she has synesthesia, but other characters have quirks in this book, too, so at the end of the day, Mia's just another teen trying to figure out how to make peace with who she is and navigate the halls of high school.