South Koreans were treated to a rare weather phenomenon on Monday when yellow snow fell in the capital and elsewhere across the country. But the snow -- containing dust or sand from the desert regions of northern China -- could pose a health hazard, the country's meteorological office warned. "It's tough to say whether it's yellow sand mixed in snow or if it's snow mixed in yellow sand," a met official told Reuters. A high concentration of the dust particles prompted the weather bureau to issue a yellow dust warning for the second time in three days. South Korea frequently...