A jet descends out of storm clouds on approach to Reagan National Airport as severe storms hit the area on Tuesday. (Jonathan Newton/The Washington Post)

Fierce storms, including a tornado, swept in waves through the Washington area Tuesday afternoon and evening, deluging some places with as much as an inch of rain in an hour and adding more commuting troubles to a region already struggling with Metro’s SafeTrack closures.

According to the National Weather Service, the thunderstorm that burst over parts of the area at 7 p.m. was the fourth of the day. Over a period of hours on Tuesday, trees toppled, lightning crackled, and thunder boomed loudly and suddenly enough to send startled office workers running to windows to see what happened.

Fallen trees and high water stalled automobile traffic at many places in the city and suburbs, and the storms and their consequences also impeded Metrorail operations.

In one of the most vivid effects of the day’s downpours, water shut down the Cleveland Park Metro station for a time. Churning cascades, descending from rain-swept streets, covered escalators to ankle depth and filled station floors with fast-flowing currents.

The station closed to passengers about 7 p.m. It reopened about 8:30 p.m.

Before the station was shut down, commuters who got off Red Line trains there took off shoes and waded barefoot against the tide.

The tornado was reported about 1:30 p.m. in western Howard County near Interstate 70 and had top wind speeds of 80 mph, according to preliminary information from the National Weather Service. It was classified as EF-0, on the Fujita scale, the lowest level, although it was strong for tornadoes of that level.

The tornado was about 500 yards wide and traveled over a path of almost 13 miles , the weather service said, based on a survey it made. Trees fell all over Howard, but there were no reports of injuries.

In the District, there were reports of a tree down in Northwest at the intersection of 16th Street and Spring Road and on Utah Avenue at Kanawha Street. The 3300 block of Military Road NW was blocked Tuesday night by a fallen tree.

By late evening, an inch of rain had been reported in Washington, almost all within two periods of one hour each.

Flash flooding was reported at the intersection of New Jersey and New York avenues NW. Piney Branch Road NW was closed by water at Beach Drive NW as of 7:30 p.m., and part of the Virginia Avenue underpass in Foggy Bottom was also flooded.

In Maryland, some of the heaviest rain came in the mid-afternoon in one of the earliest of the storms. At Baltimore-Washington International Marshall Airport, the heaviest rain came in mid-afternoon, with almost an inch between 2 p.m. and 3 p.m.

About that time, lightning struck air-conditioning equipment on the roof of the Forest Park Apartments on Piney Branch Road, the Montgomery County Fire and Rescue Service said.

Later, a house in the Aspen Hill area of the county was struck by lightning, and part of its chimney collapsed, authorities said.

Also in Maryland, there were reports of a vehicle stranded in high water at the intersection of Brookville Road and Georgia Avenue, in Montgomery County. The driver ultimately extricated himself safely, fire spokesman Pete Piringer said. To the north, a tree fell on the eastbound lanes of I-70, near Ellicott City.

Trees toppled near the Howard County, Md., fairgrounds, and in many other parts of the county, which appeared to be particularly hard hit. The fire department’s list of fallen trees extended to more than 60. At least two fell onto a houses. The trunk of one of them, a huge oak, sliced through a house for about 10 feet before coming to rest.

Some of the streets where trees fell in Howard carried seemingly apt names: They included Lightning View Road and Weeping Cherry Drive, as well as Waterford Drive and Watersville Road.

In the Bowie area of Prince George’s County, trees also toppled. One fell onto an unoccupied vehicle at the Bowie Town Center, county fire spokesman Mark E. Brady said. A tree fell onto a house in Bowie in the 12300 block of Lisborough Road. MARC train commuters faced flash-flood-related speed restrictions on the Camden-Brunswick Line, with delays of up to 15 minutes.

At Washington Dulles International Airport, a storm, one more in the day’s series, brought an inch of rain between 5 p.m. and 6 p.m. By 8 p.m. the day’s total was an inch and a half.

In Virginia, Route 50 was closed at about 2:20 p.m. in both directions, at Carter’s Farm Lane, for trees’ falling on power lines, the Loudoun County sheriff’s office said. Trees fell in the Bluemont area of Loudoun County, on Ridgeside Road.

Northwest of Annandale, in Fairfax County, water as deep as 10 inches was streaming across Woodburn Road for a time.

Automated recording devices measured one wind gust in the region of more than 50 mph.

Hailstones fell at many places, including in parts of Frederick County, Md., in the Clarksburg area of upper Montgomery and near Reston, in Fairfax County. Diameters were measured at about an inch.

The trouble wasn’t just on the ground.

Air traffic at all three Washington-area airports was stopped, with flights halted just after 1 p.m. at Dulles, BWI and Reagan National Airport, according to the Federal Aviation Administration.

At 9:30 p.m., departing flights were being held on the ground at National for between 30 and 45 minutes, the FAA said. The delay times were increasing. Delays to the New York-area airports appeared to be particularly long.

For flights arriving at National, in-air delays amounted to about 15 minutes, the FAA said.

At Dulles, an FAA website said some flights were being held on the ground for as long as three hours.

We've got warm, unstable air over the area today. Very humid, so we will have some storms likely developing this afternoon as a cold front moves in. (Jason Samenow/The Washington Post)

Airports in Newark, Philadelphia and New York also were experiencing delays.

The storms also caused power outages in the greater Washington area.

Dominion Virginia Power reported that about 6,700 customers were without power in Northern Virginia at one point, most of them in Loudoun and Fauquier counties. The number had declined to about 5,600 by 6:30 p.m. and stood at 3,400 shortly before 8 p.m.

About 9:30 p.m., Pepco reported about 2,500 homes and businesses without power. The figure represented a sharp decline from the 4,500 reported an hour and a half earlier.

At 10:45 p.m. Baltimore Gas and Electric reported that more than 14,000 homes and businesses remained in the dark.

The Maryland Emergency Management Agency reported that more than 29,000 customers were without electricity at one point in Howard County, with scattered outages in Montgomery and Prince George’s counties. At 10:45 p.m. BGE reported that more than 14,000 homes and businesses remained in the dark.

This is the second time in less than a week that storms caused delays at Washington-area airports. On Thursday, severe thunderstorms caused delays after ground stops were put into place.

As the storms swept across the area, periods of calm followed in their wake. In late evening, the orange rays of the setting sun illuminated the tops of trees and the upper stories of buildings in the city.

As 8 p.m. approached, it was light enough to see blue skies overhead. Their blue appeared particularly clear, with all the grime and dust of daily life scrubbed out. But near the horizon, dark clouds could still be detected, and the possibility of more rain could not be ruled out.