Sliding vehicles in Virginia hit six state police troopers; three of the troopers suffered minor injuries, police spokeswoman Corinne Geller said.
About 25.5 inches of snow fell at American University in Washington over two days, inching the city toward the snowfall record. The capital received 28 inches of snow in the "Knickerbocker Storm" of January 27-28, 1922.
The blizzard has left hundreds of thousands of customers from Virginia to Pennsylvania without power, utility companies said. As of 7 p.m., 92,840 customers were without power, Dominion Virginia Power said, down from 207,000 customers Saturday morning.
In Maryland and Washington, 104,331 Pepco customers were in the dark, the utility company said. The majority, or 84,829, live in Montgomery County, Maryland, and 7,643 live in Washington, according to Pepco. Another 23,163 Maryland customers were also without power, according to Baltimore Gas and Electric Co.
Are you affected by winter weather? Share photos, videosIn Philadelphia, a reported 28.5 inches had fallen at the airport by 4:45 p.m., the National Weather Service said.
"We are getting absolutely clobbered this morning with snow," said Steven Steingard, a lawyer who lives in suburban Philadelphia. "We have about a foot already and they say it will continue for 10 to 12 hours more."
In College Park, Maryland, snow-laden power lines drooped onto branches, causing power failures. One city resident, Ben Hampton, told CNN he could hear electrical transformers popping.
Annapolis, Maryland, racked up 21.5 inches of snow by 3 p.m. Saturday. State officials said 2,400 pieces of equipment were trying to clear highways. The state also was relying on 300 National Guard members to help with ongoing weather trouble.
Crews have about 12 to 24 more hours of work ahead to clear roads and ready them for the Monday commute, Maryland Emergency Management Agency spokesman Ed McDonough told CNN.
"It was coming down 2 to 3 inches an hour at times and snow plows just can''''t keep up with that," he said. In some areas, snow piled as high as 30 inches tall, McDonough said.
More than 750 personnel were clearing roads in Washington, Mayor Adrian Fenty said. But the heavy, wet snow has even trapped some plows, Washington Department of Transportation director Gabe Klein said.
Flights were canceled at the Washington-Baltimore area''''s three main airports and at Philadelphia International Airport. Amtrak has canceled many trains in and out of Washington, and Greyhound has halted bus service until 1 p.m. Sunday, Klein said.
On Friday, a weather-related accident in Virginia''''s Wythe County left two dead, state police said. A father and son stopped on a shoulder to help injured occupants of a disabled vehicle. Minutes later, a tractor-trailer jackknifed and struck their van while trying to avoid hitting the disabled car.
The father and son died at the scene, state police said.
Virginia state police said the accident was one of many crashes and disabled cars reported.
Winter storm warnings were in effect from southern Indiana eastward to New York and south to North Carolina, with blizzard warnings for Washington, Delaware and the New Jersey coast.
Delaware Gov. Jack Markell declared a state of emergency Friday night and ordered all vehicles off the roads by 10 p.m.
Forecasters were predicting that the mountains of West Virginia and Maryland, west of the nation''''s capital, would receive the most snow -- possibly 3 feet.
CNN''''s Greg Morrison, Suzanne Malveaux and Angela Fritz contributed to this report.
