Three years ago I was in the same place as you. As graduation approached, I couldn't wait to get out of my hometown. I couldn't wait to move away for college and reinvent myself into whoever I wanted to be. I knew many "lasts" in my life were happening, but I was so focused on a new beginning that I wasn't paying much attention to the ending of a major chapter in my life.
If I can tell you anything about your last summer before college, it's that you need to take advantage of it. Save up money, because no matter how many hours you work during the semester, it never seems like enough. Having extra cash is never a bad thing and you won't regret the extra hours of work you put in during the summer when you can actually afford food when you're away from home. This is probably the last summer you'll spend working with the soul purpose of saving up money. Soon you'll have to pay for tuition and bills that never seem to end. If you've been lucky enough to never have needed a job while in high school, get a part time job now. It will be hard to get an internship in college without any work experience whatsoever, so take advantage of the free time while you have it.
Take advantage of your hometown. Whether you're staying local for college or moving away, this summer may be the last summer you spend in your hometown. I never would have thought that the summer between my senior year in high school and freshman year in college would be one of my last summers in my hometown, but it was. One summer job in NYC led to two summers spent working as a personal assistant. This summer I have decided to go back to my hometown to spend my final summer break ever in the house I grew up in, but not everyone chooses to do this. Spend this summer participating in the traditions you grew up doing and at the places you love.
Spend time with family and friends. You never know where people are going to end up. While I'm about to return home for the first summer in two years, many of my high school friends will remain in their college towns. When I graduated high school, I thought that some of my high school friends would be my best friends for life. This is not the case. No friendships ended from fights, but instead faded away because of distance. So hang out with your friends and family even if it's inconvenient or you have a few episodes left of the show you're binge watching. Netflix will always be with you, but your high school friends won't.
I know not everyone will have the same experience as me, but don't forgot to take advantage of this summer. This will most likely be the last summer like all the ones you've experienced before. With internships, jobs, and college friends, you may never have a summer this carefree again. And then as soon as you know it, you're graduating from college and will never have a summer break again. Don't spend this summer dwelling on the fact that you're about to leave high school behind, but instead appreciate what you had and look forward to all of the great experiences you'll have in college. This summer may be full of lasts, but it will also lead to a lot of firsts.