The best time to visit Shannan is between April and October, when the Yarlung valley is at its most accessible and the weather is clear enough to appreciate the landscape. May and June bring mild temperatures and the barley fields are green; September and October offer settled skies and excellent visibility, with the harvest underway in the valley. Summer (July–August) brings monsoon moisture from the south, and while rain is not as heavy as in lower parts of the Himalayas, cloud can obscure views and some tracks become muddy.
Winter (November to March) is cold and very dry. Temperatures in Tsetang drop well below freezing at night, but the days can be brilliantly clear. Some sites reduce their opening hours. Tibet Travel Permits are more difficult to obtain in certain months — typically March, when the government restricts access ahead of the anniversary of the 1959 uprising — so check the current situation before planning.
The altitude throughout Shannan is between 3,500 and 3,700 metres. Budget at least two full days to acclimatise before attempting long drives or hikes.