What could have been a peaceful and relaxing week-long holiday for residents turned otherwise when northern China was again surrounded by fog and pollution on Sunday. The situation was so extreme that authorities had to suspend air flight operations as well as closed at least six expressways.

On Saturday night onwards through Sunday morning, visibility in Beijing, China's capital, fell to less than 500 metres (yards), the National Meteorological Center said. It advised residents the weather visibility disturbance would persist until Monday afternoon over northern China, including Hebei province, Beijing's neighbor.

Six expressways linking Beijing to Shanghai, Tianjin and Harbin were closed on Sunday. At least 47 flights at the Beijing Capital International Airport were forced to stay grounded.

"Air pollution will be an additional factor for holiday traveling that needs to be considered," Chen Yifeng, a Shanghai-based accountant, told Bloomberg News. "I won't go to heavily polluted places like China's north region as it's either hazardous to your health or causes trouble when traveling."

Mr Chen opted not to travel in anticipation of the long traffic and massive crowds.

Morning pollution in Humen, Donguang China pic.twitter.com/EBaHWZeQkW

— ElaineDiFolco (@ElaineDiFolco) October 7, 2013

According to the Beijing Municipal Environmental Monitoring Center, the level readings of the pollution that enveloped six of the city's core districts reached between 225-245, equivalent to a Level 5 on the pollution scale. China's highest is already Level 6, or anything above 300.

The U.S. embassy in China, meantime, had far higher readings. In an email sent on Sunday morning to American citizens in China, the embassy said that readings on the city's Air Quality Index (AQI) "have averaged over 300 in the 24-hour period beginning at 8:00 pm on October 4, and were over 400 overnight."

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