Spring (April–May) is the best season: waterfalls are running well from snowmelt and spring rain, the canyon walls are striking against green vegetation, and the temperature in the gorges is comfortable. Autumn (September–October) is the second-best season, with good foliage on Zhuyu Mountain. Summer is hot and crowded — Chinese domestic tourism peaks in July and August, and the shuttle buses and popular gorge trails become very busy. Winter can be rewarding if you are there for the ice formations on the waterfall, which can be spectacular in a cold January, but some trails close in icy conditions.
The park sees its highest visitor numbers on Chinese national holidays, particularly the Golden Week in October, when queues for the shuttle buses and the canyon trails can be lengthy. If you have flexibility, aim for a weekday in shoulder season.