One province, three climates
Yunnan is the size of Germany and spans a vertical range from tropical river valleys to the Tibetan plateau, so a single "best time" does not apply. The classic route — Kunming, Dali, Lijiang, Shangri-La — runs north and climbs from 1,900 to 3,300 metres, and each stop has its own season.
The dry season: October to April
This is the window for the plateau. Skies are clear, rain is rare, and daytime temperatures are pleasant even in January — Kunming is called the Spring City for a reason. November and March are the sweet spots: the crowds are thinner than in the holidays and the light is clean.
December and January are cold at night, especially in Lijiang and Shangri-La, where temperatures drop below freezing after dark, but days are sunny and bright. This is also when Jade Dragon Snow Mountain has the most snow and the clearest views of it.
The rainy season: June to August
Summer is the monsoon, and in Yunnan that means afternoon and evening rain rather than all-day drizzle. The landscape is at its greenest, the wildflowers on the Shangri-La grasslands peak in June, and wild mushrooms — a serious local obsession — appear in the markets from July. The trade-off is cloud: Jade Dragon Snow Mountain and Meili are frequently hidden, and road closures from landslides are possible on the northern routes.
The south
Xishuangbanna, on the Lao border, runs on a different calendar: the tropical dry season from November to April is the time to go, the Dai New Year water festival falls in mid-April, and the summer monsoon there is genuinely wet.
Holidays to plan around
The first week of October and the first week of May are the peak domestic travel weeks, and Lijiang, Dali and the Snow Mountain all hit capacity. Chinese New Year, in late January or February, brings the same pressure. If your dates are fixed, book trains and the Snow Mountain cable car the moment reservations open.