Nyingchi has a far more forgiving climate than most of Tibet. The altitude around Bayi is about 2,900 m rather than 3,600+ m, and the forested valleys trap enough moisture to create something approaching a temperate climate at lower elevations.
Spring (March–May) is the most popular season. The Nyingchi Peach Blossom Festival in March draws Chinese domestic tourists to the Niyang River valley when the orchards are in bloom. Rhododendrons follow in April and May.
Summer (June–August) is warm and lush but can bring heavy rain — the monsoon affects Nyingchi more than anywhere else in Tibet. The canyon and forest walks are beautiful but trails can be slippery.
Autumn (September–October) is arguably the best time. The weather clears, the forest turns, and Basum Tso reflects the surrounding peaks under blue skies. Namcha Barwa occasionally becomes visible.
Winter (November–February) is cold and dry. Snow closes some higher passes and Basum Tso freezes over, but Bayi itself is accessible and quieter. The peach orchards are bare but the light is clear.