And although the rains are expected to show some restraint Friday, forecasters warned that flooding will continue - and perhaps even worsen - along the Delaware and the Schuylkill.
The Delaware at Trenton is predicted to crest three feet above flood stage Friday morning. The Schuylkill is expected to creep to about 2.5 feet above at Norristown on Friday, and remain a foot above flood stage in Philadelphia into Saturday.
Thursday afternoon, New Hope declared a limited state of emergency, empowering the borough to order evacuations. Bridges to New Jersey were closed.
"The rivers are swollen, and they're coming our way," said Tom Cinaglia, public works director in flood-prone West Norriton Township, along the Schuylkill in Montgomery County.
Along with other rivers and streams from Washington to Upstate New York, the Delaware and Schuylkill have been filled way beyond their banks by the tremendous rains from the remnants of an amorphous mass of moisture named Tropical Storm Lee.
"It's never been as bad as this," said Marco Derrow, who lives with his brothers across the street from the collapsed structures in Ambler. More than 100 water rescues were reported in Montgomery County alone.
Lee, which exceeded Hurricane Irene's rainfall totals in many areas, threatened to outdo even Hurricane Agnes, the legendary 1972 storm that devastated eastern Pennsylvania. Lee already has forced the evacuations of more than 100,000 people in northeastern Pennsylvania and hundreds around here.
More than nine inches of rain has been measured this week in Wynnewood, in Lower Merion, Montgomery County, and better than a half-foot in Wrightstown, Burlington County, and in Philadelphia, where Main Street in Manayunk became a canal annex.
Jenna Batt found that out firsthand Thursday morning. The commute from her Mount Airy home to the Manayunk beauty shop where she works typically takes 15 minutes. "It took me a little under two hours," she said. When she finally made it, she learned that her son's school was closed, meaning she had to go back to get him.
As of late Thursday, Lincoln Drive remained under two feet of water, and Kelly Drive was closed for road repairs, said Capt. Thomas Helker of the Philadelphia Police Department's traffic division. Kelly Drive might be closed until Sunday.
The stream and river crests turned out to be more vigorous than anticipated earlier in the week.
In Yardley, rescue workers helped residents leave 15 homes in the flooded River Mawr neighborhood, Code Enforcement Officer Wes Foraker said.
"This was worse than Irene. The water is two feet higher," Foraker said.
Area streams prone to flash flooding have been particularly jumpy. The Brandywine Creek, for example, burst out of its banks in Chester County, engulfed Route 30, and made it impossible to get from one side of Downingtown to the other Wednesday night.
More than 40 residents of an Avondale apartment complex had to be evacuated to a shelter set up by the Red Cross at Avon Grove High School in West Grove, a county spokeswoman said.
Haverford Township, Delaware County, declared a state of emergency as cars were stranded by rising waters. All schools were closed, and residents in the Wynnefield Drive area were offered shelter at Linwood Elementary School.
About 40 residents of Maple Avenue, in the hard-hit section of Whitpain Township, Montgomery County, near Ambler, took shelter in an American Legion post.
Derrow and his brothers, John and Giuseppe, said they were awakened early Thursday by water seeping into their duplex. Before long, firefighters were fanning the street pulling people out of their homes. As of Thursday, 7.69 inches had fallen this week in Ambler.
"Cars parked in the roads were flipped over," John Derrow said. "The firefighters were dragging people out. Some people are worried they'll condemn all our homes."
The creek-side flooding should subside Friday, as the forecast calls for less-robust showers, with rainfall totals of a quarter-inch or less.
The region could use a break. The 3.65 inches that fell Thursday in Philadelphia was a record for the date, and since Monday, 6.35 inches has been measured at Philadelphia International Airport. That brings the 2011 total to a staggering 48.48 inches, just over four feet. In 138 years of records, that total would put 2011 in the top 20 for precipitation for any calendar year - even if another drop doesn't fall until the ball drops on New Year's Eve at Times Square.
The Lee-related rains have been episodic and almost random in the immediate Philadelphia area, said Gary Szatkowski, meteorologist at the National Weather Service in Mount Holly. That explains why some areas have been hit harder than others.
The rains also received an extra measure of juice from Katia, which is off the Atlantic Coast, and that added to the totals, said Jeff Masters, meteorologist with Weather Underground, a forecasting service.
The situation along the Delaware River Basin hasn't been as traumatic as it is in the Susquehanna's, where rains have pounded even more consistently, Szatkowski noted. Thus the mass evacuations.
"It's bad here," Szatkowski said. "It's extreme there."
Contact staff writer Anthony R. Wood at 610-761-8423 or firstname.lastname@example.org.
Contributing to this article were Inquirer staff writers Jeremy Roebuck, Mari A. Schaefer, and Kathleen Brady Shea.