Tibet has a vast land. Its climate zone can be divided into the tropical, the subtropical, the temperate and the frigid. Climates are much different in different areas in Tibet and temperatures vary greatly within a single day. Climate in southeastern Tibet is gentle and temperate with the average temperature of eight degrees; in western Tibet, the average temperature is below zero degree; While in Lhasa and the central part of Tibet, the climate is normal and nice for traveling. Visitors will not feel cold in winter not hot in summer, especially from March to October, the best seasons for traveling. Most annual rainfall comes in the rainy season that starts from May to September, when the precipitation covers 90 percent of the whole year. Usually it rains at night in Lhasa, Shigatse (Xigaze) and Chamdo area. The precipitations gradually decrease from 5000 millimeters in the lower part of southeast to just 50 in the northwest. Spring and winter are the 'dry season' or 'wind season' which starts from the last third of October and ends in the next April. During this time, hardly rain comes to this highland. Winter is snowy, dry and cold, starts from November to January.
Compare with most parts of China, air in Tibet is thin. Per cubic meter air only has 150-170g oxygen, just occupies 62% or 65.4 of that in the lower altitudes; oxygen content is about 70% (in one cubic meter air), while summer is about 80%.
Most of Tibet is a high-altitude desert plateau over 4000m (13,123ft) and many passes exceed 5000m (16,404ft). Days in summer (June to September) are warm, sunny and dry, from low to mid 20℃ (70-75℉), but temperatures drop quickly at night. Winter is not as cold as you might expect, still averaging around 7°C (44℉) during the day in January but plunging to around -10℃ (14℉) at night. The best time to visit depends on what part of Tibet you're heading to, but for most areas May, June and October are the best months.
Renowned as the "sunshine city", Lhasa enjoys an astounding annual sunshine time of 3,000 hours. The most comfortable seasons to visit Lhasa are in summer and fall. The city is also unique for its "night rain" and sunshine during the day. Lhasa is about 3658m / 12001 feet above sea level.
Average Maximum Temperature of Lhasa
Average Minimum Temperature of Lhasa
Lhasa /Shigatse /Lhatse /Tingri /Nyalan: Along the Friendship highway is basically in good conditions year around. But from December to February, the thawed road could make some trouble. Try to avoid August - landslide could happen in the rainy season.
Mt. Everest Base Camps Area: Early May and early October are the best time to visit Mt. Everest Base Camps. Due to the clear weather, you have great chance to see Mt. Everest Base Camps's true face (if you are lucky). From December to February, you'd better not to go to this area because it is too cold - except you are real Great Adventure People.
Ali (Mt.Kailash): Even without climate restrictions, this area is already inhospitable. Big rain and snow could make the journey worse. However, for those determined tourists, the appropriate time is May, June, July, September and October.
Eastern Tibet: Don't go to this area in July or August (the rainy season) because the rain could ruin the road, and make terrible landslides. In winter, the road could be frozen.
Northern Tibet: With the average altitude of 4,500m, this area offers very limited time for tourists. Summer (July to August) is the prime time to enjoy the great plain in northern Tibet.