What is the best time to visit Yellowstone?

Although Yellowstone National Park is open year around, certain times are better to visit than others. The park is primarily open from May to October, with the months of July and August attracting the largest number of visitors. May, June and September are somewhat less crowded, and the weather during this time can still be a bit cool due to Yellowstone’s high altitude. For winter visitation, the months of January and February are best.