Buildings are shrouded in smog in Zhengzhou, capital of central China's Henan Province, Jan. 4, 2015. China's top meteorological authority forecast medium to severe smog in the country's northern regions including Beijing and Tianjin as well as the neighboring Hebei Province on Sunday. Meanwhile, smoggy weather will also affect the country's eastern province of Jiangsu as well as the southwestern province of Sichuan on Sunday. (Xinhua/Feng Lei)