Huge Sandstorm Turns Beijing Sky Orange

China's capital woke up to orange-tinted skies today as the strongest sandstorm so far this year hit the country's north, delaying some flights at Beijing's airport and prompting a dust warning for Seoul. The sky glowed and a thin dusting of sand covered Beijing, causing workers to muffle their faces in vast Tiananmen Square. The city's weather bureau gave air quality a rare hazardous ranking.

Air quality is "very bad for health," China's national weather bureau warned. It said people should cover their mouths when outside and keep doors and windows closed. China's expanding deserts now cover one-third of the country because of overgrazing, deforestation, urban sprawl and drought. The shifting sands have led to a sharp increase in sandstorms—the grit from which can travel as far as the western United States. (More China stories.)