WASHINGTON (AFP) - A huge snow storm stretching from St Louis to Washington on Monday grounded hundreds of flights and left shivering residents wondering when winter would finally give way to spring.

Nearly a week after the spring equinox, huge swaths of the United States remained deep in winter's clutches. Temperatures hovered well below freezing and snowplows and shovels were pulled back out of sheds.

The National Weather Service forecast that five to eight inches (13-20 cm) of snow could fall on the nation's capital, Ohio, Pennsylvania and New Jersey while mountainous areas of West Virginia and Kentucky could get as much as 16 inches.

"Isolated power outages may occur because of snow-laden wires and tree limbs," the weather service warned. "Road signs will be covered with wet snow.

Snow removal may be dangerous for those with heart conditions since it will be wet and heavy."

Indiana already received as many as nine inches in some areas and another three inches were expected before the storm blew over on Monday afternoon.

Lighter dustings were expected in several other states.

Meanwhile, St Louis was digging out from a record-breaking 12.4 inches of snow which fell on Sunday and continued to accumulate on Monday.

The storm led to the city's horse racing track to delay its season opener for the first time in its nearly 100-year history after the snow left dangerous ruts in the track.

"The primary concern is always the safety of the horses and jockeys," Mr Darrel Cassity, assistant race secretary at Fairmount Park Race Track, told the St Louis Post Dispatch.

Roads in the New York area were expected to be a slushy mess as wet snow fell, even as temperatures remained just above freezing.

Some 536 US flights had been cancelled by midday on Monday, according to FlightAware.com, with New York, Philadelphia and Washington topping the list.