For first-time Tibet travelers, a frequently asked question is when is the best time to visit Tibet. Well, that is a bit difficult to answer for it depends on many factors. But usually speaking from April to October is suitable for tourism each year, and from June to August is the best traveling time. In winter all tourist sites except Namtso and Yarlung Tsangpo Grand Canyon are open to visitors as usual.
From April to October, all local attractions are open to visitors, Green leaves make a shade and there is sufficient oxygen. Most travel agents offer daily departure tours and you will have more tour options.