A useful guide on when is the most popular/ seasonal time to visit the United States National Parks. Use this to plan for the best time to visit when the National Parks will be open or go when there will be less crowds in the National Parks. Includes Acadia, Arches, Zion, Big Bend, Bryce, Yosemite, the Rocky Mountians, Mt Rainier, and other National Parks. Most parks are open 24/7 but have some operations closed in the winter so do your research before visiting!