A dense wave of smog began Process_start in Northeast China , especially in major cities including Harbin , Changchun and Shenyang , as well as the surrounding Heilongjiang , Jilin , and Liaoning provinces on 20 October 2013 .

The smog eased on 25 October 2013 and had completely dissipated Removing by the 28th due to a cold front that had moved Motion in from Russia .