A resident takes a boat on a river Thursday in Tongzhou district of Beijing. Photo: Fu Zengkai

Fog shrouds trees Thursday in Tongzhou district of Beijing. Photo: Fu Zengkai

Shenyang, northeast China’s Liaoning province, issued a red alert, the highest level, on Thursday as the fog reduced visibility to less than 20 meters in some parts of the city. Photo: IC Photo

A resident crosses a street in the fog Thursday morning in Shunyi district of Beijing. The weather agency of the city has issued orange fog alert, the second-highest level, on Thursday as the fog reduced visibility to less than 50 meters in some areas. Photo: VCG

Residents ride together on a scooter Thursday in Binhai New Area of Tianjin, where the fog caused traffic jams. Photo: IC Photo

Residents send their children to schools in dense fog Wednesday morning in Handan, North China’s Hebei province. Sections of over 30 highways across the province were closed due to low visibility caused by the fog. Photo: IC Photo

A resident crosses a street in the fog Tuesday in Urumqi, northwest China’s Xinjiang Uygur autonomous region. Photo: Liu Xin/China News Service, IC Photo

Heavy fog shrouds buildings Tuesday in Urumqi. Photo: Liu Xin/China News Service, IC Photo

A resident works out wearing a mask Wednesday in Lianyungang, East China’s Jiangsu province. Photo: VCG

A resident rides a scooter Wednesday in Binzhou, East China’s Shandong province. Photo: IC Photo

Vehicles drive in the fog in Shunyi district of Beijing on Thursday morning. Photo: VCG

Heavy fog shrouds a highway Thursday morning in Beijing. Photo: VCG

Thick fog covers the urban area of southwest China’s Chongqing municipality on Wednesday. Photo: Chen Chao/China News Service, IC Photo

Vessels sail on the Hanshui River in the fog Wednesday in Wuhan, Central China’s Hubei province. Photo: VCG