Woman in a smoggy street

Photo: STR/AFP/Getty Images

Smog season returns with a vengeance

A woman wearing a protective face mask on Oct. 21 walks along a smoggy street in Harbin, China. Visibility dropped to 33 feet after choking clouds of pollution blanketed the northern city, which is famous for its annual ice and snow sculpture festival.

China's smog is at its worst in the winter months when coal plants go into overdrive to provide power and heat to the people. Last year's off-the-charts air pollution was so bad that the government ordered 180,000 heavily polluting vehicles off the roads.

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Catie Leary is a photo editor at Mother Nature Network. Follow her on Twitter and Google+.