Alert renewed for northern China

Some areas in northern China are likely to see another day of smog as the national observatory issued an orange alert for air pollution on Sunday. Heavy smog was expected to stay in some parts of Beijing, Tianjin, and Hebei, Shandong, Henan and Shanxi provinces from Sunday overnight to Monday morning, according to the National Meteorological Center.

Central and southern Hebei will see PM2.5 density higher than 500 micrograms per cubic meter of air with visibility reduced to less than 200 meters, according to the center. Meteorologists forecast a cold front will help disperse the smog later Monday.

China has a four-tier color-coded system for severe weather, with red being the most serious, followed by orange, yellow and blue.