The snow - up to 10 inches in some parts of South Jersey - was not expected to last, as the National Weather Service predicted rain for Monday, though there's a chance of more snow Tuesday.
Forecasters had called for two to four inches of snow Sunday.
"We had a relatively narrow band of quite heavy snow," said Al Cope, a meteorologist with the National Weather Service in Mount Holly.
"We were getting very heavy snow at rates of two to three inches per hour that lasted for two to three hours in some places. The snow added up pretty quickly. It was definitely a good bit more than we had anticipated," Cope said.
The heaviest snow fell in northern Delaware, which got 11 inches. There were reports of eight to 10 inches across South Jersey, he said.
Despite the storm's being more severe than expected, the Philadelphia School District planned to open Monday, spokesman Fernando Gallard said.
NJ Transit said to help ease the Monday commute, it would allow customers to use any NJ Transit ticket or pass on rail, light-rail, or bus routes, including private bus carriers.
U.S. Sen. Cory Booker (D., N.J.), who rose to fame as Newark mayor by once shoveling residents' snow, on Sunday tweeted an offer to a resident of Burlington County.
Booker, who has 1.4 million followers on Twitter, was asked via tweet: "Can you come dig us out in Mt. Holly?"
Booker replied: "If you still need the help tomorrow. I will stop through on my way to DC."
Driving became a hazardous affair throughout the area as steady snow turned roads slick.
The Pennsylvania Department of Transportation had planned on one to four inches of snow by early evening, but by noon it was clear a major storm was underway, spokesman Gene Blaum said. The agency boosted the number of trucks on the road to 415 from 300 in a bid to get ahead of the rapidly falling snow.
The fatal turnpike accident happened about 12:30 p.m. near the Morgantown interchange in Berks County.
When the man who had gotten out of his car was struck, it caused a domino effect of accidents involving more than 50 vehicles in a 12-mile stretch of the turnpike, spokesman Carl DeFebo said.
The rapid succession of crashes disabled many vehicles, but only one of the occupants involved in the fender-benders required hospitalization, DeFebo said.
SEPTA's biggest problem Sunday evening was the northbound Manayunk/Norristown Regional Rail line. Trains between Miquon and the Norristown Transportation Center were able to use only the inbound line because of a frozen switch.
"At the moment, I don't see anything that will last into the morning," spokesman Manny Smith said.
This article contains information from the Associated Press.