Snow, sleet, freezing rain and perilously cold temperatures forecast to sweep eastern two-thirds of nation

More than 500,000 households and businesses in the US are without power and more than 9,600 flights are expected to be cancelled ahead of a monster winter storm that threatens to paralyse eastern states with heavy snowfall.

Forecasters said snow, sleet, freezing rain and dangerously frigid temperatures would sweep the eastern two-thirds of the nation on Sunday and into next week.