Tibetan climate is not as harsh as many people imagine it to be. It is suitable for travel to Tibet from April to the beginning of November, and the best time is August and September. But if you only stay in Lhasa, you can go there anytime of the year.
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.
Current Weather Forecast Lhasa, CN: