Passengers at the square of Nanjing Railway Station during a hazy day in Nanjing, Jiangsu province, Jan 18, 2013. [Photo by Dong Jinlin/Asianewsphoto]

BEIJING - China's top meteorological authority on Sunday continued to warn of smoggy weather that has battered parts of China for days.

The National Meteorological Center (NMC) issued a yellow alert for smog on Sunday morning, the fourth straight day such an alert has been announced.

Smog will persist in the day time in parts of Hebei, Tianjin, Shandong, Henan, Jiangsu, Anhui, Shanghai, Zhejiang, Hubei and Hunan, the NMC said.

The NMC advised people in the affected regions to wear masks. It forecast that smog will ease on Monday thanks to a moderately strong north wind, which will lead to a drop in temperature.

China's meteorological disaster alerts are categorized as blue, yellow, orange and red as the severity of disasters ascends.