The best time for you to go to Tibet is between July and September. Tibet has intensive polar radiation, long duration of sunshine and low temperature, along with decreasing temperature decreases as altitude increases. Tibet is also characterized by a division of humid and dry seasons with most of its rainfall in the nighttime. In Tibet, the winter is dry, cold, windy and long; the summer is mild, rainy and it hails often. Generally, the four seasons are not distinctive. In most parts, the average temperature in the hottest month is below 15℃ and the average temperature in January and July is between 15℃ and 20℃, which is lower than that of any part of the eastern plain at the same altitude.
The seasonal factor must be considered when traveling to Tibet. In certain regions the winter is long while the summer is short. There are few areas in southeastern Tibet that have comparatively distinctive seasonal changes. In districts like Lhasa, Xigaze, Nyingchi and Shannan, the transportation is convenient so you can visit any time of the year. Districts like Qamdo with poor transportation should be visited in May, June or September.
Spring and autumn are the best seasons to visit the Ali district. In summer, the travel to the south is bumpy and in winter it is not easily accessible after snowing.
In the spring it is cold and damp in the Nyingchi district. In autumn, it is the most comfortable season and the scenery is great for visitors.
In the Changdu district, flights to the city of Changdu are available, but during the rainy season the road condition are bad.
In northern Tibet, apart from the Qinghai-Tibet highway, it is unlikely you can make it to the Lake District. It is windy and dusty in spring. Autumn is the best time for traveling, but it is a short season. In winter, the road conditions are good unless there is snow.