The following are parking alternatives from the UNH Parking website.
Summer students can purchase permits to park in surrounding student lots: https://www.unh.edu/transportation/student-summer-permits
There are also many "pay and display" kiosks around campus. One is on Main Street, the road on which Hamilton-Smith Hall is located, the home of Summer Institutes. Here is a link to explore this option: https://www.unh.edu/transportation/parking/visitor-parking