The best time to visit Rocky Mountain National Park is from June to September when the snow is (mostly) melted and the hiking trails and attractions are accessible. Still, these four months are also the most popular times to visit, so if you'd rather experience RMNP in relative isolation and while wearing snowshoes or cross-country skis, visit between the months of October and May. Whether snow or sunshine, the park is open to the public 24 hours a day, 365 days a year, though some parts may be inaccessible.