The US east coast's worst snow storm in four years blanketed the region with heavy snow and ice Thursday, closing down much of the federal government and grounding air traffic. According to dpa, the storm has claimed at least 12 lives and shut off electricity to more than half a million customers from Georgia and South Carolina into the northern states, CNN reported. In the Washington region alone, up to 40 centimetres of snow fell through the night and plows struggled to keep up or even got stuck. All area schools were closed and major roads were empty of traffic. Sleet and rain were to follow, turning back to snow as another weather front moves through Thursday night and into Friday. The National Weather Service warned that roads would be "hazardous" up and down the east coast.