The Beijing-Tianjin-Hebei area and neighboring regions in northern China have been shrouded by heavy air pollution since Sunday.

The National Meteorological Center announced a yellow alert for heavy fog on Monday morning, warning that southern Beijing, southern Tianjin, central and southern Hebei Province, northern Henan Province, northern Shandong Province and many areas in central China will encounter heavy fog, with visibility of less than 1,000 meters.

According to Beijing authorities, the whole city reached the fifth level of the air pollution scale on Monday, the second-highest level in the six-tier system. It means that the average density of PM2.5, fine particulate matter, was between 150 and 250 micrograms per cubic meter of air.

The National Meteorological Center forecasts that the smog is expected to weaken on Tuesday accompanied by strong wind and cold air. Before the smog is swept away, it's not recommended to travel around in the above-mentioned regions.

(Cover image via VCG)