In Bucks County, sections of Upper Southampton, Lower Southampton, and Northampton Township sustained the most damage.
"I've lived here since '57 and nothing like this," resident Tom Kunts said.
Various homes sustained water damage to their basements and had to be pumped out Monday. Much of the day was spent drying out and assessing damage.
About two dozen people rescued from their homes spent the night in shelters, reports CBS station KYW-TV.
In the Pittsburgh area, power is back on for 13,000 homes and businesses. Sunday night's storm knocked out power in Pittsburgh and its surrounding towns of Wilkinsburg, McKeesport and West Mifflin. Most customers had power restored within a few hours of the storm.
Duquesne Light spokesman Barry Kukovich says crews are bracing for more outages over the next couple of days as storms continue.
Although Bucks County in suburban Philadelphia had some of the heaviest damage, it was far from alone.
In northern Columbia County, heavy rains washed out a bridge and caused a mudslide Sunday night.
Emergency management director Walter Brasch said a metal bridge on Route 254 just south of Benton was washed out, and a mudslide occurred on Talmar Road in Pine Township.
Brasch said the storms dumped more than five inches of rain on the Benton area, while the rest of the county received less than an inch.
Little Fishing Creek and Green Creek overflowed their banks.
There were also reports of basement flooding as a result of that heavy rain caused by the thunderstorms.
And in the small town of Salisbury, about 55 miles southeast of Pittsburgh, firefighters were kept busy dealing with the flood.
Storm drains in Salisbury could not handle the four inches of rain that fell Sunday, Fire Chief Heath McKenzie said, so the water began backing into basements, and homeowners called firefighters to pump the water out.
Salisbury was doused with a two-hour cloudburst.
In Elk Lick Township, the storm washed shale, rocks and mud out of a paving project into a nearby road.
Volunteer firefighters from Maryland were called in to help with the problems.
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