Reservations along the coast from June through September are essential. As others have said, the state parks will be full and many private parks will be as well. Some areas do not have a lots of options/spaces to start with and summertime travel is gorgeous making these parks very popular. In the "good old days" you could just wander in.............no more. Also, Wal-Marts do NOT allow overnighting along the coast. Make your reservations and enjoy the trip.