Smog will persist in eastern China until Monday, though it will disperse in northern China on Sunday, according to the China Meteorological Center.

A cold front on Sunday will bring strong winds and clean up northern China. Temperatures will drop by 6 to 8 degrees Celsius in and to the north of the central and lower reaches of the Yangtze River.

Smog in Shanghai, Jiangsu and Zhejiang will persist until Monday.

The center on Sunday morning upgraded its smog alert from yellow to orange, warning of serious smog in western Jiangsu, northern Zhejiang, eastern Anhui, southeastern Hebei and western Shandong.

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