Photo courtesy of the California Travel and Tourism Commission/Andreas Hub. 1  Summer is the most popular time to visit the park, when all roads are open and a variety of outdoor pursuits are possible. Just be prepared for big crowds, elbow jostling on trails, jam-packed campgrounds and 'No Vacancy' signs at park lodgings. Spring is another busy time, when Yosemite Valley's waterfalls peak during April and May. Early in spring, some park roads will still be closed by snow (see the opening information), but valley campgrounds are open and lower-elevation hiking trails are passable. Plan your trip here. Fall is Yosemite's shoulder season, with fewer crowds.