File photo: Xinhua

BEIJING, Feb. 13 (Xinhua) -- China's national observatory on Saturday renewed a yellow alert for heavy fog in parts of the northern, central and southwestern regions, as well as some coastal areas.

Thick fog is expected to hit parts of Beijing, Tianjin, Hebei, Henan, Anhui, Hubei, Hunan, Jiangxi and Guizhou through Saturday morning, according to the National Meteorological Center (NMC).

Visibility in some affected areas will be reduced to less than 200 meters, the NMC said.

The observatory also forecasted heavy fog in parts of the Bohai Sea, the Yellow Sea, and coastal regions off the Bohai Bay, the Liaodong Peninsula, the Korean Peninsula, the Shandong Peninsula, Jiangsu Province and the Hangzhou Bay on Saturday, which will reduce visibility in some areas to less than 1 km.

The NMC said drivers should slow down to safe speeds while airports, freeways and ports should take appropriate safety measures.

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