Business accounts of students with outstanding fines are held until payment in full is made for these fines. The fines don't go away. It is very risky to carry an outstanding ballance. Cars parked in certain illegal situations risk being towed. There are very very few accepted excuses that will get you out of a ticket, so it is important to avoid them before getting them, and to pay them if you do.
Parking is enforced to some extend every day of the year.
During summer, winter, and spring breaks, the university is still open and therefore ALL rules and regulations remain in effect.