The monster storm, dubbed "Snowpocalypse" and "Snowmageddon," stretched hundreds of miles from eastern Indiana across into Pennsylvania and then down through Maryland as far south as North Carolina.

With winds gusting at almost 90 kilometers an hour, meteorologists said they had recorded snowfall as high as 96 centimeters in parts of northern Maryland - a historic high for the state.

The heavy, sticky snow toppled trees and sagged power lines, leaving more than 350,000 people without electricity in Maryland and neighboring Virginia, officials said.

"Snowmageddon here in DC," President Barack Obama told Democrats in a speech, only a year after chiding the capital city for its cautious response to small snowfalls.

Forecasters warned residents to hunker down, with no let-up in the weather for most of the day, and said chilly temperatures on Sunday would mean the wet snow would swiftly turn icy.

"It's hanging on, and hanging on," Paul Kochin, an expert in northeast weather systems with the National Weather Service, said.

"Officially this won't break records in DC, but unofficially, you bet it will. It's very rare to have two such big storms in one season," he said, after the capital region was already crippled by a smaller storm in December.

Maryland, followed by neighboring Virginia, were bearing the brunt of the storm and seeing the highest snowfalls, he said.

"It's pretty rough out there," agreed Ed McDonough from the Maryland Emergency Management Agency.

"The roads are very difficult to travel... and we are seeing a spike in power outages. We are telling local residents to stay home, enjoy the time with their families and let the highway crews do their work."

Emergency crews struggled to repair the power outages hampered by the miserable weather.

"We have a lot of scattered outages and the road conditions are not really working with us," admitted Pepco spokesman Andre Francis, pleading for patience as some customers were told the blackouts could last days.

Some 200 National Guardsmen had been deployed across Maryland, while in Virginia police confirmed that a father and son were killed Friday when they stopped to help a stranded car.

Police in the state had responded to some 3167 calls for help, more than two-thirds of which were due to car accidents or stranded vehicles.

Three state troopers were also injured in storm-related accidents. Virginia was also opening up public shelters in local schools for those without power.

In the normally bustling capital, sight-seers were walking thigh-deep in the snow along the famous national mall.

Alix Lawe, who works with the US Air Force, was out for a run in the snow, and said: "It's so fun. I'm from Florida, I've never seen so much snow."

Snow plows were out trying to keep emergency routes and main highways clear, but most officials said it would take days to reach the smaller streets, and warned of a difficult Monday morning commute.

The National Weather Service (NWS) has put the Washington-Baltimore metropolitan area under a rare 24-hour blizzard warning until 10pm (local time).

All flights out of the capital's Reagan National airport were canceled, along with most flights out of Dulles International Airport in Virginia, while there was a limited service at Baltimore.

A hangar roof collapsed at the Dulles Jet Center early Saturday according to Rob Yengling, Metropolitan Washington Airports Authority spokesman. Five people spending the night inside to shelter from the storm escaped without injuries.

The capital's subway system has shut down 40 above ground stations, meaning transport links between Washington and its heavily-populated suburbs were snapped with most major roads impassable, knocking out bus services.

But some people were determined to enjoy the winter's second biggest storm in the area, with 5000 turning out for a mass snowball fight in central Washington.