Factual error: When Cecelia and her friends are in the car, following Aquamarine, Hailey, and Claire to the water tower, they aren't that far away - probably less than thirty feet - yet the other girls don't hear their car approaching.
Factual error: The film is based in Florida but several scenes show rocky cliffs and hills not native to the area.
Answer: Most likely, Aquamarine and her father had argued multiple times, about her not wanting marry the boy that he chose for her. She was going against tradition. Claire's grandmother probably saw storm signs caused by an earlier argument. Then Aquamarine's father got angry enough to make the big storm.