Tibet is high altitude plateau set amid tall mountain ranges all around. The mountain ranges catch the rainfall before it reaches the basin, so most of Tibet except the southeastern area is a desert steppe, tundra or permafrost. So generally expect cold and dry weather.
Most of Tibet experiences frost at least 6 months of the year, and the highest lakes have ice except from about about October to March. The weather varies a lot from region to region, and Lhasa (elevation 3,490 meters (11,450 ft)) is ideal for tourists to the region because it is in a lower elevation area valley in the warmer and wetter central and southeastern part of the country.
Lhasa only gets about 68% of the oxygen at sea level, so altitude sickness is a problem for most visitors. The valleys of Lhasa, Shigatse, Gyantse, and the Brahmaputra are free from permafrost and are well cultivated. See weather information for Dingri, Shigatse, Tsetang, and Lhasa
Most of the territory has a cold, dry and harsh climate. The annual precipitation in Lhasa is relatively higher at 500 millimeters (20 inches), and the annual precipitation across the region averages between 100 and 300 millimeters (4 and 12 inches). January is the driest and coldest month at -9 °C (16 °F) with virtually no snow.
A monsoon affects Tibet from June to September. August is the wettest month with a moderate 120 mm (5 in) in Lhasa.
Bright sunshine (the Lhasa valley gets 3,000 hours of sunshine a year) helps to make the summer days pleasant. The high altitude and dry air makes Tibet feel warmer than the temperature during the day.
In the summer Lhasa experiences a temperature range of between a pleasant 10 °C (50 °F) and 23 °C (74 °C). The hottest month is June with an average high temperature of 23 °C (74 °F).
Generally speaking the best months to visit Tibet are from May to October, when the weather is not really cold, averaging above 10°C. This is naturally the busiest travel time in Tibet.
July and August is therainy season in Tibet, though, apart from in the southeast, there is still not a lot of rain. If you go camping or trekking ideally avoid these two months. The best months for camping are May and September when it hardly rains at all.
If you plan to travel to Mt. Everest, travel in April, May, September, or October, when you are more likely to see the peak clearly. It is more likely to be hidden behind thick clouds the rest of the year.
Travelers who are interested in Tibetan festivals are recommended to visit Tibet in August when the Shoton Festival, Nagqu Horse Racing Festival, and Ganden Thangka Festival are held. But expect to see huge crowds during the festivals.
Late September to October is the best time to see autumnal colors in Tibet.
Weather: Spring is from March to May. In May, the ice begins to melt, and people can start to travel to higher areas or other valleys. In Lhasa, the average high temperatures average about 16 °C or 60 °F.
Clothing: Coats are necessary. Bring a pair of sunglasses. Tibet will be closed to foreign travelers from February to March in 2014.
Weather: Summer is from June to August. It is usually cool and dry. It occasionally rains. The summer rainy season is widely regarded as the "best time” of the yearsince it rains mostly at night and Lhasa is still sunny during the daytime.
Things to do: Summer is the time to travel to the various attractions in the region and enjoy the high altitude sites when the mountain passes are snow free. It is also a time to hike a little.
Tibetans hold their outdoor market fairs and encampments, festivals, and sports contests when the grasslands are their lushest. Festivals of note include the Ganden Thangka Festival, the Shoton Festival, and the Nagqu Horse Racing Festival.
Clothing: Bring a coat and long johns. Sunglasses and solar skin protection is necessary.
Weather: Autumn is from September to November. The weather is cold with lows at the lowest elevations of -4 °C (23.2 °F). So warm clothing is necessary. In October and November, there is negligible precipitation.
Weather: Winter is from December to February. Road travel is difficult because the passes may be closed, but tourists can enter Lhasa via the airport.
Around Lhasa, the average low temperature is -9 °C (15 °F) at night, but there may be warm spells also. The high altitude dry air makes it feel warmer than the temperature.
Winter is considered the low tourist season, so the hotel and tour rates are cheaper than usual. Getting train tickets to Lhasa is also much easier than in summer.
Clothing: Bring a coat, long johns, and gloves. Wearing layers is a good idea. Bring sunglasses.
Special seasonal highlight: The Tibetan New Year usually falls between late December and February. Streets will be colorfully decorated for the event in the cities.
Winter is not suitable for traveling around Tibet as the weather is freezing and windy. People are more likely to suffer serious mountain sickness in harsh winter.
*Note*:Tibet will reopen to foreign travelers in April. Book a Tibet tour before the summer tourist crowds arrive.