Beijing's meteorological authorities issued an orange alert for smog at 5:50 p.m. Thursday, forecasting visibility of less than 500 meters from Thursday night to Friday morning.
Meteorological authorities issued yellow alerts for heavy air pollution on Tuesday and Wednesday.
In China's four-tier severe weather warning system, red is the most serious alert, followed by orange, yellow and blue.
On Thursday, environmental authorities launched inspections on key construction areas in the city, with illegal activities found in 19 spots.
Bad weather conditions will see air quality get worse in Beijing and north China from Thursday to Saturday.
