A man flies a knight in Pudong district in Shanghai, shrouded by smog on Dec 6, 2013. [Photo/icpress.cn]

BEIJING - Lingering smog in the country's central and eastern regions is expected to end on December 9, according to the China Meteorological Center (NMC).

The NMC has upgraded the alert from a yellow alert to the more serious orange alert for worsening smog in these regions.

Heavy smog swept China's central and eastern regions in early December. Some of the regions experienced three to five days of smog, while Jiangsu, Zhejiang, Anhui and Henan provinces had suffered lingering smog for six consecutive days.

A weak cold front on Saturday will do little to reduce the smog, the NMC forecast.

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

The good news is that a cold front with gale-force winds is expected to sweep China on Sunday and clear the smog. Temperatures will drop by at least 6 to 8 degrees Celsius from Sunday to Wednesday.