Beijing: The Chinese capital and its surrounding provinces were once again covered by highly polluted smog, disrupting highway traffic and flights, officials said on Sunday.
Beijing Environmental Protection Monitoring Centre said PM 2.5 -- hazardous particles measuring 2.5 microns in diameter or less -- exceeded 238 micro grams per cubic meter in some areas.
The US Embassy`s air quality index reading stood at 265 micro grams which is classified as "very unhealthy".
Moderate to serious air pollution was reported in many parts of Beijing, with a visibility of no more than 500 meters in early morning, the centre added.
The visibility at Beijing Capital International Airport at one point fell to 5 to 10 meters, delaying some flights, state-run Xinhua news agency reported.
The expressways linking Beijing to other cities including Kaifeng, Harbin, Shanghai and Tianjin were temporarily closed, Beijing Municipal Traffic Administration authorities said.
The provinces of Tianjin, Hebei and Henan were also affected by heavy smog today.
The air quality index reached 500, or extreme pollution, in five monitoring sites at 8 am in Shijiazhuang, the provincial capital of Hebei.
Prolonged smog hit many Chinese cities in January and has returned periodically, turning out to be a major health hazard.
Meanwhile a strong cold snap is set to bring temperature down in most parts of China in the coming three days, together with strong winds and snow affecting the holiday travel peak, the National Meteorological Centre (NMC) said in its forecast.
The temperature is expected to drop by six to eight degrees Celsius from today through Tuesday in some regions of southwest China, areas south of the Yangtze River and most parts to its north, accompanied by winds of level four to six, the NMC said.
Some areas will see temperatures plunge by ten to 12 degrees, according to the observatory.
Although the week-long Lunar New Year holiday officially ended on Friday, the NMC and the Ministry of Transport (MOT) warned about traffic safety in affected regions as many travellers are still on their way back to work.
Meanwhile, sections of a few national highways across northeast China and Tibet Autonomous Region are being affected by heavy snow, the NMC and MOT said in a joint statement.