A car is partially submerged on Rhode Island Avenue NW during the storm. (Boundary Stone Public House)

Intense rain, fueled in part by the remnants of what had been Hurricane Isaac, pelted parts of the Washington region Sunday, flooding low-lying spots and cutting some Metro rail service, amid reports of rescues of trapped motorists.

By about 9 p.m., 3.5 inches of rain had drenched the grounds of Children’s Hospital in Northwest Washington, according to The Post’s Capital Weather Gang. Parts of the city from the Capitol to American University got at least 2 inches of rain.

Severe street flooding was reported in the city’s Bloomingdale neighborhood, which has flooded at least four times this year. Water rose over the wheels of cars, and a segment of Rhode Island Avenue was closed.

“They rescued a man from out of a car,” said Eddie Ellis, who lives in the 200 block of Rhode Island Avenue NW, a block west of the flood zone.

Three cars were stalled in the 100 block of Rhode Island Avenue NW, said John Sollers, chief of the D.C. fire department’s special operations battalion.

Flooding in the Shaw-Howard University Metro Station. (Ana Santos)

He said the vehicles’ five occupants reached safety either on their own or with the aid of firefighters.

Although the street rapidly came to resemble a river, and an inflatable boat was brought to the scene, those in the cars “were never in any immediate danger,” Sollers said.

For some residents of the area, the flooding was made no easier to bear by the fact that they had seen it before.

“I’ve got about 10 inches of water in my basement right now,” said Larry Holeman of the 500 block of Florida Avenue NW. “I’m so disgusted.”

Water cascaded into the Shaw-Howard University Metro station, forcing Metro to halt service until just before midnight on part of the Green and Yellow lines.

Water was flowing between the rails in the station, and two other stations on those lines, Columbia Heights and U Street, were also shut down. Trains were stopping at Georgia Avenue on one end of the affected zone and at Mount Vernon Square on the other.

The thunderstorm parked itself over Northwest Washington, and scarcely moved as it soaked the city. In addition to Bloomingdale, the Adams Morgan and Mount Pleasant neighborhoods, among others, were deluged.

“It’s definitely wet and wild up here,” an Adams Morgan resident told the Capital Weather Gang.

While this was happening, about 7 or 8 p.m., many parts of the area apparently recorded no rain at all.

But the water had scarcely receded in the District when a new line of storms swept into Northern Virginia. They were headed in a northerly direction and were capable, the National Weather Service said, of producing heavy downpours.

Much earlier in the day, weather concerns prompted a decision to relocate the National Symphony Orchestra’s annual Labor Day concert on Sunday. Scheduled for the Capitol’s west lawn, it was moved inside the Kennedy Center.

Storms had been rolling through the area since Saturday. Officials at the Maryland State Fair in Timonium said a concert there Saturday night was shut down “due to lightning in the area.”

Remnants of Isaac were expected to continue affecting the Mid-Atlantic region into Wednesday, the Weather Service said.

On Saturday, rainfall at Reagan National Airport was measured at 1.64 inches. That rain, which fell in two hours, made Saturday the wettest day of the year, as officially measured at the airport.