BEIJING - China's meteorological authorities issued a blue-coded alert for heavy fog in the country's southern areas on Saturday.

Visibility will be reduced to less than 1,000 meters in Jiangsu, Jiangxi, Zhejiang, Fujian and Hunan provinces and even less than 200 meters in few regions, the National Meteorological Center (NMC) forecast.

People ride bikes amidst heavy fog in Nanchang city, the capital of East China's Jiangxi province, Jan 26, 2013. [Photo/Xinhua]

The alert represents the lowest level after red, orange and yellow in China's four-tier color-coded weather warning system.

In the next 24 hours, a fresh weak cold air will sweep eastern part of northwestern China, areas along the Yellow and Huaihe rivers and south of the two rivers, bringing strong winds and dropping temperatures by 2 to 4 degrees Celsius, the center said.

The NMC also expects moderate to heavy snowfall to hit Xinjiang Uygur autonomous region, Inner Mongolia autonomous region and Northeast China's Heilongjiang province in the coming three days, while some parts of southwestern China will see light to moderate rainfall.