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 the Main Street, the road on which the building housing the Summer Institutes is held. Here is a link to explore this option: https://www.unh.edu/transportation/parking/visitor-parking