China issues alerts for heavy fog

China's top observatory on Sunday issued yellow alerts for fog in north and eastern regions. China has a four-tier warning system for bad weather, with red being the most serious, followed by orange, yellow and blue. From Sunday night to Monday morning, heavy fog will reduce visibility to less than 500 meters in some areas of Hebei, Shandong, Anhui, Jiangsu, and Zhejiang, according to the National Meteorological Center. During the same period, moderate smog will shroud some areas in north China and east China, while sleet and snow will hit some parts of northwest China.