A drenching, lightning-filled thunderstorm, the heaviest downpour in 23 years to hit Washington on July 4, halted the National Independence Day Parade in the District and disrupted other celebrations but retreated in time for the man-made fireworks to proceed as planned on the Mall.

A hardy crowd, smaller than in previous years, sat on soggy blankets and lawn chairs or stood in the mud to watch the intricately shaped American, Chinese, Italian, Japanese and Spanish pyrotechnics flash high in the rain-cleansed sky. The 1.6 inches of rain that fell in the area earlier soaked band uniforms, turned portable toilets into shelters and boosted sales for umbrella-hat vendors.

Heavy rains, such as those in 2001, have threatened the celebrations before, but the Mall fireworks have not been postponed since 1979. That rainstorm yielded only 0.19 inches, but officials decided to play it safe and wait a day. In 1989, a 1.28-inch rainstorm hit on the Fourth of July, according to the National Weather Service, but the fireworks went off on schedule. The last rainfall measuring as much as 1.6 inches on July 4 occurred in 1981.

The crowd, worried that last night's show might be canceled, came alive when the Capitol Fourth 2004 concert began at 8 p.m., and some in the audience sang along or waved flags to the music. The fireworks brought squeals from children, and many of their parents aimed camera phones at the brightly bursting shells.

They were still in the mood when they joined long lines waiting to enter the Archives-Navy Memorial Metro station. Some college-age men began singing "The Star-Spangled Banner" a cappella, and many in the crowd, including Metro Transit Police officers, joined them. "I've been doing this since 1975, and this was one of the most moving moments I can remember," said Chief Polly L. Hanson.

Yesterday's rain flooded some parts of the Capital Beltway, forced the postponement of at least two suburban fireworks shows and prompted some Mall visitors to leave for their homes or hotels before the evening festivities. By 8 p.m., 237,669 people had ridden Metrorail; by that time last year, ridership was at 339,597.

The parade down Independence Avenue, which began at 11:45 a.m. with 11 marching bands and a dozen floats, was halted by National Park Service officials a half-hour later with only 28 of 86 groups having finished the 10-block route. "There are supposed to be bad cells of hail and lightning," parade producer John Best said. "We're disappointed, but the safety of the participants and the street crowd comes first."

Many of the 3,000 parade participants tromped into the nearby museums for shelter. The Smithsonian's National Museum of American History let members of marching bands store their instruments in the basement. Kyle Wannigman, 17, a drummer at Los Alamos High School in New Mexico, dried off in the cafeteria next to a sandwich line that stretched 40 yards.

"It's lots of work and lots of fundraising to just turn around and go home," he said. Many band members had taken off their wool uniforms and stretched them out to dry, hanging them over the backs of chairs.

"We smell like wet dogs," Wannigman said.

A group of friends from Kansas and the Washington area didn't let the weather keep them from their sixth consecutive Fourth of July celebration on the Mall. "Hey, we're 98 percent water," said Robert Baylor, 38, of Arlington, referring to the human body. He and his friends arrived at 10 a.m. to put up a 25-by-13-foot party tent, which they festooned with 10 U.S. flags and several state flags.

Each year, Baylor said, more friends show up, bringing flags from their home states, to watch the fireworks from near the Washington Monument. Some took off their T-shirts and basked in the rain, while others tossed a football. "This is the best seat in the house for the best fireworks show in the nation," Baylor said.

The Mall was closed early in the morning as authorities conducted a security sweep. Then 19 security checkpoints were opened for anyone who slogged through the wet grass and mud. Although the national terror threat level remained at yellow, or elevated, for the holiday weekend, security was tightened, as it has been for both July 4 celebrations since the Sept. 11, 2001, terrorist attacks. In May, Attorney General John D. Ashcroft and FBI Director Robert S. Mueller III warned that the Independence Day celebration was among major public events that terrorists could target this year.

More than 20 local, state and federal agencies helped provide security yesterday. District police activated 14 surveillance cameras and joined U.S. Park Police to staff checkpoints along the Mall.

Some shelter was offered by the Smithsonian Folklife Festival, which featured tent-covered performances and demonstrations by musicians, dancers, crafters, storytellers and artists focusing on this year's festival themes -- music in Latino culture, Haiti and mid-Atlantic maritime communities.

But other visitors had to improvise to stay dry. The Frasure family from Columbus, Ohio, huddled in a blue portable toilet for handicapped users, the only one big enough for Terri and her children Sara, 10, Joshua, 26, and Isaiah, 15. They had set up their coolers and chairs for fireworks viewing nearby, but by 2 p.m. they had left other family members to take refuge in the outhouse.

They hoped to stay for the fireworks. It was their first Independence Day in Washington, and they had driven from Ohio on Friday. "It's always been important to us to have our freedom," Terri Frasure said.

People braving the downpour also stimulated rain-gear sales. Guy Foster, 43, wore one of the red, white and blue umbrella hats he was selling as he wished passersby a happy Fourth. "Last year, I was just selling flags, but a homeless woman was selling these," said the D.C. resident, pointing to the hat. "I'm doing excellent."

At the Mall, many visitors vowed to stay for the fireworks, rain or not. "What's our option? Going back to the hotel?" asked Yamuna Fiorentino, 25, a teacher from Hillsborough, N.C. "That's boring."

Rob McGee, 38, a teacher from Mount Holly, N.J., stuck a U.S. flag next to his beach chair between Seventh and Ninth streets. "It's a chance to shut out politics for half an hour," he said after the fireworks.

Rex Ryan, 41, and his son, Peyton, 12, had to wait to board the Metro at Federal Triangle for the ride home, but the fireworks show "was definitely worth it," Peyton said. "It was really cool. I've never seen any fireworks any bigger. It was neat. The fireworks were really humongous. It was amazing."

Elsewhere in the city late last night, some residents set off fireworks that resulted in a bang of a different sort. Desk officers at police stations in several neighborhoods reported a surge in complaints, many from elderly people about illegal fireworks. Only sparklers are legal for personal use in the city, said Alan Etter, a spokesman for D.C. Fire and Emergency Medical Services Department.

But neighborhood revelers at least avoided some of the crowds at the far larger celebration on the Mall. At an elevator leading to the Federal Triangle Metro station, it was shoulder-to-shoulder traffic, and those pushing baby carriages weren't necessarily guaranteed a spot in the elevator. "The people walk right over you. This is insane -- we have a baby in a stroller," said Michelle Ward, a mother of three from Williamsburg.

Her eldest daughter, 8-year-old Cyndal, said she was prepared to stay up late.

"Mommy and Daddy were telling us we were going to get home very, very late," Cyndal said. "I think I am going to be very worn out and very tired tomorrow."

Fireworks enthusiasts watch the luminous display on the Mall from along Jefferson Drive NW.With Julia Lambert in a stroller and Katherine Byers on her back, Annette Auchten trudges through Constitution Avenue and 15th Street NW after the Independence Day Parade was cut short.Kylah Boykin, 3, and her grandmother Marsha Boykin watch the fireworks spectacular over West Potomac Park from the steps of the Jefferson Memorial. It was Kylah's first fireworks show.From behind columns at the Jefferson Memorial, a classic view of the fireworks as well as the Washington Monument. Mall fireworks have not been postponed since 1979. Fireworks illuminate the Lincoln Memorial, as viewed from across the Potomac River in Rosslyn. A few communities canceled their shows.