Winter, spring, summer & autumn are major seasons. Winter from December to February Tibet Introduce it self a remote isolated country. Major highway, roads, trail cover the snow. Air China, Air China Eastern close its flight Schedule between mainland China and Kathmandu during winter. From end march to end of October, flight operates from mainland China and from Kathmandu to Lhasa. All tours in Tibet initiate from March to November. March and November Kathmandu to Lhasa, return to Kathmandu overland trip possible. From middle of May to the middle or end of September. In fact for the month before the monsoon hits, and for the month after it has officially receded, the weather patterns are similar, so the following applies nearly the whole time that we run trips. The monsoon washes over Tibet sometimes bringing brief showers of rain and lots of cloud but mostly the main Himalayan chain stops the real monsoon from reaching Tibet. Tibet is mostly fine for the whole year and it is very rare for it to be covered in thick cloud, rather big, fluffy clouds often in the afternoon. Sometimes these obscure views but often they don't, merely add to the whole panorama. If you would like to combine Tibet Tour and Nepal Tour at same time March April, May and October is recommended. June, July, August & September rains most of time in Nepal but in Tibet doesn't rain much.