Yellow alerts for fog in China's many regions were issued on Thursday by the country's central observatory.

From Monday night to Tuesday morning, heavy fog will reduce visibility to less than 500 meters in some areas of Beijing, Tianjin, Hebei, Shandong, Henan, Jiangsu, Hunan, Jiangxi, Guizhou, Guangxi, Fujian, Yunnan and Sichuan, according to the National Meteorological Center.

China has a four-tier warning system for bad weather, with red being the most serious, followed by orange, yellow and blue.