The Tibetan climate is not as harsh as many people imagine it to be. The best time of year to be in Tibet is from April to the beginning of November, after which temperatures start to plummet.

Tibet is cold in winter, cool in summer and generally dry, receiving only 450 millimeters (18 inch) of rain or snow. Sunlight is extremely intense. The thin air neither blocks nor holds heat, and temperature can vary greatly within a day, exceeding 29degrees in desert areas in summer, and plunging below 4 degrees the same night.
The central Tibet, including Lhasa, Gyantse, Shigatse and Tsedang, generally has very mild weather from April to November, and the most annual rainfall comes in the rainy season that starts from June to September. Usually it rains at night in Lhasa, Shigatse and Chamdo area. The rainfall may block roads and make travel difficult but the scenery at the time will be the best.
October and November often bring some dazzling clear weather and daytime temperatures can be quite comfortable at Tibet's lower altitude.

The coldest months are from December to February. It is not impossible to visit Tibet in winter. The low altitude valleys of Tibet (around Lhasa, Shigatse and Tsedang) see very little snow.

Spring does not really get under way until April, though March can have warm sunny days and is not necessarily a bad month to be in Tibet.
Most annual rainfall comes in the rainy season that starts from June to September. Usually it rains at night in Lhasa, Shigatse and Chamdo area. The rainfall may block roads and make travel difficult but the scenery at the time will be the best.