Smog shrouds the China Central Television building in Beijing on Monday, when severe air quality prompted the capital to order polluting industries to suspend production. [Photo/Agencies]

BEIJING - China's weather observatory upgraded its fog alert from yellow to orange, second most serious level, for Saturday evening to Sunday morning.

Fog will be thickest in Hebei, Shandong and Henan with visibility less than 200 meters, according to the National Meteorological Center.

Visibility will be less than 500 meters in Beijing, Tianjin, Jiangsu, Anhui, Hubei and Hunan.

Snow will disperse smog on Monday and Tuesday, while rain will sweep some parts in southern China.

The public has been warned to take protective measures when engaging in outdoor activities, and those who suffer from respiratory diseases are advised to stay indoors.