With an altitude of 3650 meters (11,975 feet), Lhasa is one of the highest cities in the world. It has the highland temperate semi-arid monsoon climate. Annual rainfall here is considerable and mainly falls from the June to September Most of the time it rains at night. The air in Lhasa is thin and the temperature is comparatively low. The temperature differences during a single day can be large. Comparatively from March to October, the climate becomes mild and humid: this is the best season to travel in Tibet. The spring and winter in Lhasa are dry and windy. Generally the May Day Holiday is the beginning of the traveling season.