How does you daughter feel about sitting in on a class? For the first round of visits, many find they are still determining what type of school they would like. Local visits are good for getting the feel of the school. If she likes the local schools, she would have time to sit in on a class fall of senior year, or do an overnight, if they remain on her list. We found the schools further away take more thought and planning.
For my S18, we did further visits spring break his junior year, and then again summer between junior and senior year. Summer is not ideal, but you can still determine the definite no’s. We visited five over the summer and he decided two stayed on with eventually applying to one as he changed his mind about majors and one was not strong in his major. You asked if there is a better time in the summer. Check the school calendars as some may have a special summer day. If she is interested in one specific school, it may be worth it to try and match up the trip with those days.
Good luck and enjoy the journey. A lot changes in a year and it will go by fast!!