The East Coast is gradually digging out from the record-breaking snowstorm that battered the East Coast Wednesday night, causing power outages and leaving travelers and commuters stranded.

It was the sixth snowstorm to slam into the region in the last 30 days.

Overnight, thundersnow -- the rare phenomenon in which thunder and lightning strike even in the dead of winter -- shocked residents in Sellersville, Pennsylvania, and as far away as central New Jersey. Philadelphia was hit with 17 inches of snow, totals in the Washington D.C. area ranged from 3 to 7 inches and, according to the National Weather Service, parts of New Jersey had to dig out from 19 inches.

In New York City, officials declared a weather emergency and all public schools were closed for today.

The city received about 19 inches of snow in what is now the snowiest January in more than a century of record-keeping. The average winter in New York City brings 21 inches of snow; this year there have been more than 50.

In Washington, D.C., the snow prompted officials to close government buildings and schools in surrounding areas. It also left more than 400,000 people in and around the nation's capital without power.

The Boston area was hit hard by the storm as well, receiving about a foot of snow.

Michael Eckhart of the National Weather Service said several other states felt this storm's wrath.

"The snow from this system extends from eastern Tennessee and western North Carolina all the way up to Maine, so it's hitting especially the major population along the I-95 corridor," he said.

Transportation Mess

The latest snowstorm caused transportation problems up and down the East Coast.

New Jersey state police have reported more than 500 accidents.

The Long Island Rail Road in New York is operating on a reduced schedule.

In Washington D.C. and Maryland, abandoned cars and buses lined the roads.

ABC News' Vic Ratner endured the heavy, wet snow on this ride home to suburban Maryland from the District Wednesday night.

"I spent about five and a half hours with about 75 other people on a crowded bus. We were all trying to get home. but the road was littered, in places impassable," he said.

Air travelers are encouraged to check with their airlines for delays and cancellations due to the storm.

New York's John F. Kennedy International Airport and New Jersey's Newark Liberty International Airport were closed for snow removal until 10 a.m. LaGuardia Airport cancelled 168 flights. At Philadelphia International Airport 1,500 passengers were stranded overnight, according to airport spokeswoman Victoria Lupica.

Snowstorms Bust Budgets

The record-breaking winter in the East Coast has caused cities to go over budget on snow removal -- with nearly two months of winter yet to go.

New Jersey has already spent more than its $20 million budget.

Tennessee set aside $14 million, and has actually spent $20 million.

Boston has already used two-thirds of the $16 million allocated for snow removal.

New York City spent almost all of its $38 million budget before the first of the year because of the blizzard that hit the day after Christmas.