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China's national observatory on Sunday forecast smog to hit north China in the next few days. Starting Monday, moderate smog will cover Beijing as well as southern Hebei Province, the National Meteorological Center (NMC) said.

It advised the public to take precautions, and patients with respiratory diseases were told to reduce outdoor activities.

Meteorological experts expect north China to face more smog this autumn and winter due to unfavorable weather conditions.

Beijing aims to keep average PM2.5 levels below 60 micrograms per cubic meters in 2017. Its density of PM2.5, a key pollutant, decreased by 12.5 percent year on year to 63 micrograms per cubic meter from January to August.

Meanwhile, heavy rain will sweep the country's southwest and the Huanghuai region in the next three days, said the NMC.