Hubei, which lies in the middle Yangtze River valley, derived its name from its location north of the Dongting Lake. It is also known as the "thoroughfare of nine provinces": with the Yangtze River flowing from west to east and the Beijing-Guangzhou Railway running from north to south, Hubei is located right in the middle of the country's main water and land transport artery. It has an area of 185,900 sq km and a population of 56,540,000. The provincial capital is Wuhan. Hubei has a sub-tropical monsoonal climate, with distinct contrast between the eastern plain and the western mountainous area. It has a mean annual temperature of 15°－17°C. and sticky weather in the height of summer. With its absolute maximum temperature exceeding 40°C, Wuhan is one of the hottest places in China. The mean annual precipitation increases from 800 mm in the northwest to 1,500 mm or more in the southeast.