Pittsburgh emergency responders throw a life vest to Robert Bailey, 80, who climbed onto the roof of his car after being caught in a flash flood Friday in Pittsburgh. Three people died in a flash flood after heavy rains submerged cars in the area around Washington Boulevard.

PITTSBURGH — Flash floods submerged more than a dozen vehicles in Pittsburgh, killing three people, leaving another missing and presumed dead, and forcing others to swim to safety or scramble onto the roofs of their cars.

The flooding occurred after a pair of storms pounded the city on Friday, overwhelming the drainage system and causing manhole covers to pop off the road, officials said. Water rose up to 9 feet in some places along Washington Boulevard, a main road that parallels the Allegheny River in the city’s Highland Park section.

Rescue crews used inflatable boats to reach marooned drivers, though some swam to safety on their own. Rhodearland “Bob” Bailey of Penn Hills, 80, was rescued from the roof of his car.

“I can swim a little bit and was looking at a tree branch,” Bailey told a Pittsburgh newspaper. “I heard one woman yelling for help, but the water was coming down so fast, I couldn’t see. ... I’ve never seen nothing like this in my life. Lord have mercy.”

The area received 2.1 inches of rain in an hour during the evening rush, said Rihaan Gangat, a meteorologist for the National Weather Service. But an earlier storm meant the region was drenched by 3 to 4 inches of rain overall on Friday.

The three victims, a woman and two children whose names were not released, were unable to escape their vehicle, which was submerged and pinned to a tree, Pittsburgh public safety director Michael Huss said at a news conference.

Rescuers floated over the car without knowing it was below.

“The bottom of the boat didn’t even scrape against the top of the car,” said Raymond DeMichiei, deputy director of the city Office of Emergency Management.

A fourth person, a 70-year-old woman, was missing and presumed dead, Police Chief Nate Harper said.

Harper said 18 vehicles were stranded in the high water and 11 people were rescued. One of the rescued women required hospital treatment.

The water had receded by Friday evening, but the mud-caked road remained closed Saturday as emergency crews worked to clear all the stranded cars.

Tara Howes, 34, of Gibsonia, told the newspaper that “manhole covers started popping up and it looked like the road exploded and the waters came up really fast. I saw people swimming on the sides of the road. It was pretty scary.”

The flash floods hit an area that experienced serious flooding last month. Rushing water from a July 18 storm stranded motorists and caused a section of Washington Boulevard to buckle.

Claudia Gallagher, who was driving north on Washington Boulevard at the height of the rainfall Friday, said she tried to get off the road as the water rose.

“We tried to drive up onto the curb, but the water had other ideas,” Gallagher, 55, of West Mifflin, told a newspaper.

Her car began to float, and she opened her window and climbed onto the roof. Many other drivers nearby were sitting atop their cars, too, she said.

Earlier Friday, another storm caused power outages that led the University of Pittsburgh to close for the day. Parts of Carlow and Carnegie Mellon universities also lost electricity.

Flights at Pittsburgh International Airport were grounded because of lightning just after 3 p.m., spokeswoman JoAnn Jenny said.