Several parts of northern China are likely to see another day of heavy smog. The national observatory has issued an orange alert for air pollution.

Weather authorities say heavy smog will stay in some parts of Beijing, Tianjin and the provinces of Hebei, Shandong, Henan and Shanxi until Monday. Parts of Hebei province will experience a PM2.5 density higher than 500 micrograms per cubic meter of air.

An orange alert means heavy pollution. This alert is triggered when the density of PM2.5 particles in the air is higher than 150 micrograms per cubic meter for three consecutive days. But cold temperatures will help disperse the smog later on Monday.