Climate in Tibet
The Tibetan plateau, and particularly the south, is not as cold as you might imagine. With the exception of high passes, the snow, even in winter, rarely stays on the ground for more than a few hours. The days are generally warm and it is only at night that temperature can drop drastically. Rather than cold, it is the extreme dryness of the air that characterizes Tibetan weather. Nearly all the rain falls in the summer months.
In the sheltered valleys of Lhasa, Tsetang, Kongpo, and southern Kham, the winters are mild and beautiful. From December to March is the pilgrimage season to Lhasa and in many respects, this is one of the best times of the year to visit.
The eastern regions are more prone to the weather patterns of S.E Asia. During August, it can be quite wet, and although this is a very good time of the year to attend secular and religious festivals, travelers should be prepared!