Extremely heavy fog in several Chinese provinces on Thursday led to dangerously low visibility, closing highways, delaying flights out of Shanghai and prompting weather forecasters to release a string of warnings and advisories. Dense fog affected Shandong, Hubei, Hunan, Jiangxi and Fujian provinces with visibility below 200 m (656 ft) while some parts of southern Jiangsu and southern Anhui had visibility below 50 m, China's National Meteorological Centre said. The Central Meteorological Observatory issued yellow and orange warnings for heavy fog up to 7:45 a.m. (2345 GMT).