China lies mainly in the northern temperate zone under the influence of monsoon winds．From September and October to March and April the following year，monsoon winds blow from Siberia and the Mongolia Plateau into China and decrease in force as they go southward，causing dry and cold winter in China and a temperature difference of about 40 to 45℃between the north and south．The temperature in China in winter is 5 to 18℃lower than that in other countries on the same latitude in winter．Monsoon winds blow into China from the ocean in summer, bringing with them warm and wet currents，thus rain. Great differences in climate are found from region to region owing to China’s extensive territory and complex topography. The northern part of Heilongjiang Province in Northeast China has no summer，Hainan Province has a long summer but no winter；the Huaihe River valley features four distinct seasons；the western part of the Qinghai—Tibet Plateau is covered by snow all the year round；the southern part of the Yunnan—Guizhou Plateau is spring—like all the year round；and the north-western inland region witnesses a great drop of temperature in the day．Annual precipitation also varies greatly from region to region：it is as high as 1，500 millimeters along the southeastern coast．Decreasing landward，it is less than 50 millimeters in Northwest China.