By the time commuters were getting ready to venture home Wednesday, a colossal traffic jam already was developing - in the atmosphere.
A cluster of showers moved into the Philadelphia region at midafternoon, and then, "it just kind of stopped," said Valerie Meola at the National Weather Service in Mount Holly.
The result was the region's wettest spring day in 142 years of record-keeping, widespread major flooding along suddenly chocolate-brown waterways, a rash of water rescues, streets more suitable for kayaks than cars, and prodigious cleanup chores likely to lap into the first weekend of May.
More than a half-foot of rain - or two months' worth - fell on some areas, and flood warnings remained posted for the Schuylkill from Philadelphia to the Norristown area, the site of major flooding, into Thursday afternoon.
No serious injuries or deaths were reported, but thousands of the region's residents are likely to spend more time scraping mud off their properties than tending flower beds this weekend.
The worst of the flooding occurred west of the Delaware River. But in New Jersey, just about any place prone to flood - the Admiral Wilson Boulevard and the Cooper River, or Lumberton's Main Street - did so.
Thursday morning, motorists who dared to drive on flooded highways in some cases regretted it.
"Individuals that tested their fate realized they made a mistake, weren't successful, and got stuck," said Camden County Parks Director Frank Moran.
Abandoned cars could be seen on North and South Park Drives, which border the Cooper River in Pennsauken and Collingswood, where the water slowly receded through the day.
At the Pennsauken Boathouse, rowers were told there would be no practice Thursday and there was no access to boat ramps that in some cases had broken during the surge.
"All of the docks were impacted, and we closed the river today because of debris," said Jamie Stack, boathouse manager.
Thick tree limbs could be seen in the middle of the Cooper, which Stack said was the racing channel and would have to be cleared before a competition Sunday.
In the nearby park, a playground was submerged in several inches of water, picnic tables had floated away, and pools of water covered the grass where gaggles of geese normally gather.
Marquis Diggs, 26, and his girlfriend, Kyiesha Pinto, 23, of Camden, walk around the park regularly and were surprised.
"This is a first," Diggs said. "I've never seen it flood this big."
About 900 students could not get to Camden public or charter schools by bus Thursday morning because of flooding, district spokesman Brendan Lowe said.
Mass transit agencies experienced disruptions.
In Lumberton, the siren at Fire Company No. 1 on Main Street went off about 4:30 a.m., warning of rising flood waters.
The rain had swollen the South Branch tributary to the Rancocas Creek that goes through town, and the creek was passing over its banks.
"We jumped when we heard the siren go off," said Tom Harrison, 35, who lives in the 500 block of Main Street with his wife and two children.
He said he walked through knee-deep water in his backyard and quickly moved the family's two cars to higher ground.
"This morning, I said, 'I have waterfront property,' " he said as he held his 22-month-old son, Hunter, in his arms. "We have three feet of water in the basement and we're pumping it out now."
Wendy Donegan, 32, and daughter Julia, 6, walked along a closed Main Street to see the overflowing creek and property damage. Living on nearby Chestnut Street, they were unaffected by the flood.
"It's sad to see people go through this again," she said, referring to other floods over the last 10 years.
Other Burlington County towns hit hard included Maple Shade, Cinnaminson, and Mount Holly, where the municipal court was closed because of flooding, said county spokesman Eric Arpert.
Arpert said the water had receded in most places Thursday, but officials would watch for problems at high tide.
Gloucester County Freeholder Heather Simmons, liaison to the county's public works department, said that area was largely unscathed, with some flooding in backyards and streets.
"A little bit of minor flooding, but nothing that we don't usually see," Simmons said. "We fared very well."
Across the river in Chester County, emergency officials reported 65 water rescues. Along the Brandywine Creek at Chadds Ford, the water was so deep that two large Dumpsters had floated away from Fellini's Cafe on Baltimore Pike.
Some of the worst flooding occurred on the Schuylkill in the Norristown area and downstream into Philadelphia, shutting both the Kelly and Martin Luther King Drives on Thursday.
A SEPTA bus was nearly submerged after it got stranded in Manayunk, requiring firefighters to rescue the driver and two passengers Wednesday night.
The Schuylkill at Norristown crested seven feet above flood stage.
"This is one of the worst ones I've seen out here," said Jefferson Fire Company No. 1 Chief John Bergstrasser in neighboring West Norriton Township, one of the most flood-prone communities in the region.
Officially, 4.81 inches of rain was measured at Philadelphia International Airport, and the 4.42 inches that fell on Wednesday represented records for an April 30, the month of April, and the entire spring.
"We were kind of heading toward drought conditions," said Tony Gigi, a weather service meteorologist in Mount Holly, noting the recent outbreak of brush fires.
"This will put an end to the fire season."
Contributing to this article were Inquirer staff writers Jan Hefler, Angelo Fichera, Ed Colimore, Joseph A. Gambardello, Laura McCrystal, Julia Terruso, Bob Moran, Allison Steele, Chris Palmer, Mark Fazlollah, Aubrey Whelan, and Anthony R. Wood.