A bird's-eye view of China would indicate that China's terrain descends in four steps from west to east. China abounds in rivers. More than 1,500 rivers each drain 1,000 square km or larger areas. More than 27,000 billion cu m of water flow along these rivers, 5.8 percent of the world's total. China has a marked continental monsoonal climate characterized by great variety.
Northerly winds prevail in winter, while southerly winds reign in summer.
The four seasons are quite distinct. The rainy season coincides with the hot season. From September to April the following year, the dry and cold winter monsoons from Siberia and Mongolia in the north gradually become weak as they reach the southern part of the country, resulting in cold and dry winters and great differences in temperature. The summer monsoons last from April to September. The warm and moist summer monsoons from the oceans bring abundant rainfall and high temperatures, with little difference in temperature between the south and the north.