China is characterized by a continental climate. The latitude spans nearly 50 degrees. The greater part of the Chinese territory is situated in the Temperate Zone, its southern part in the tropical and subtropical zones, and its northern part near the Frigid Zone. Temperatures differ therefore rather strikingly across the country. The northern part of Heilongjiang Province has long winters but no summers; while the Hainan Island has long summers but no winters. The Huaihe River valley is marked by distinctive seasonal changes, but it is spring all year round in the south of the Yunnan-Guizhou Plateau. In the northwest hinterland, the temperature changes dramatically. China¡¯s high tundra zone is situated in the Qinghai-Tibet, where the temperature is low in all four seasons. Some desert areas are dry all year round.