BEIJING, Feb. 5 (Xinhua) -- China's national observatory on Tuesday renewed a yellow alert for thick fog that will hit parts of the country.

Thick fog will be seen in parts of Anhui, Chongqing, Hubei, Hunan and Jiangsu in the morning, reducing visibility in some areas to less than 200 meters, the National Meteorological Center said.

The center said drivers in the affected regions should slow down, while airports, freeways and sea ports should take appropriate safety measures.

Starting from Wednesday night, cold air and high wind will dissipate the fog gradually from the north to the south and bring down temperatures by 6 to 10 degrees Celsius in most parts of central and eastern China.

Heavy snow is expected to hit northern parts of Xinjiang and southern Tibet in the next three days. Moderate snow and sleet will be possible in nothern and northeastern China as well as the eastern part of the northwest region.

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