Cities in North China are forecast to experience another two spells of smog in the coming weeks due to windless weather, but not as severe as the one that enveloped Beijing since Nov 27, the national weather authority said on Thursday.

The first spell is expected to arrive on Tuesday and last for three days before a new cold front arrives, said Liu Hongli, a researcher at the Chinese Academy of Meteorological Sciences.

He added after the wind, a second spell of smog may come between Dec 14 and 16, covering the vast region of northern China including Beijing, Tianjin and Hebei province.

Xue Jianjun, senior engineer of the National Meteorological Center agreed, adding that the two spells of smog would occur between the intervals in wind, and southern cities in the Beijing-Tianjin-Hebei region may have severe air pollution during them.

On average, the trilateral region will not have smog as severe as that which covered the region late last month until the wind dispersed pollutants on Wednesday, Xue said.

The capital has seen the concentration of PM2.5 – particulate matter with a diameter of less than 2.5 microns – off the charts, exceeding 945 micrograms per cubic meter on Sunday.

The national safety level for the PM2.5 concentration is 75 micrograms per cubic meter.