Beijing issued its highest-level warning for excessive pollution for only the second time ever on Friday, as China's north braces for at least four days of thick smog.
According to the country's National Meteorological Centre, the smog will begin Saturday evening and last until Tuesday, affecting several areas including the northwestern city of Xian and the northeastern cities of Shenyang and Harbin.
Beijing's first-ever red alert was issued by the government just last week, when pollution levels climbed to 300 micrograms per cubic meter and as high as 976 in certain areas.
