One hundred florists summoned from across America are arranging 230,000 inaugural blossoms in the basement of the D.C. Armory. Fresh white lines are painted and seven miles of steel crowd-control cables are strung along Pennsylvania Avenue. Hoteliers and caterers are working overtime to prepare for more than 20,000 guests and scores of lavish parties. And city inspectors have put the seal of approval on the presidential comfort station.

The nation's capital yesterday dug itself out, dusted off a four-inch blanket of snow and then resumed the feverish final preparations for the festivities of the 50th Presidential Inauguration -- starting with a fireworks spectacular on the Mall tonight that kicks off three more days of pageants, parades, parties and pomp.

As thousands of jubilant Republicans began arriving here for President Reagan's four-day victory celebration, a team of thousands of workers from the D.C. government, the Secret Service, the armed forces, and private contractors completed two months of detailed planning. Yesterday, they put finishing touches on arrangements for food and drink, transportation and entertainment, and tactics to combat everything from snow to rain to power failures to terrorist attack.

"We're just about ready," said Joseph Yeldell, head of the D.C. government's inaugural task force. But the mood was more hectic at the Presidential Inaugural Committee, which bears the burden of running the show, coordinating 22 events and keeping it all within a projected $12 million budget.

"There's a minicrisis an hour," said William Henkel, the White House troubleshooter dispatched to pull together the thousands of details and blend them into America's quadrennial political gala that climaxes Monday when Reagan takes the oath for his second term during public ceremonies at the Capitol.

Within the Presidential Inaugural Committee, the game plan is to assure a "quality event," chairman Ron Walker's favorite phrase. At yesterday's 10 a.m. senior staff meeting, Walker, puffing away at cigarettes, his body literally vibrating energy, got the good news and the bad from his lieutenants.

Three city-wide channels for the committee's walkie-talkie system were set. Ticket glitches were being handled by an "error resolution team" near ticket will-call at the D.C. Convention Center. And treasurer Fred Hale, who'd been rating committee finances on a scale of 1 to 10 since November, but had never gotten past 7, told him: "By 4 o'clock today we can call it a 10."

"Now I can breathe a real sigh of relief," Walker asserted, and the room broke into applause.

But all was not rosy.

"I am dealing with the horse-dropping issue," said parade director Dan Denning, charged with guiding the record-breaking contingent of 730 horses through the city. Said Denning: "I want everyone to know, there is no way to deal with the problem completely."

Walker, only half-joking, inquired: "Do we have any numbers" on the volume of droppings?

"Yes sir," said Denning. "Sixteen-and-a-half tons." City public works crews, he said, will deal with the aftermath.

Despite careful planning, not everything went smoothly at the inaugural ticket office at the convention center -- at least not for some out-of-town guests such as Roger Campos, 38, a Phoenix electronics executive who had purchased $5,000 worth of inaugural tickets to entertain his clients. Or so he thought.

"They don't have my tickets," said Campos, chairman of Arizona's branch of the Republican National Hispanic Assembly. Campos, whose firm has Defense Department and other government contracts, planned to entertain Mexican and Canadian business clients during the inauguration celebration, which he called "the biggest social event of the next three years."

"It's getting a little nervous," said Campos, after an apologetic committee aide assured him he'd get his tickets Friday.

Within the D.C. government, officials generally professed a calm assurance that all was under control. Virtually the entire 3,500-member police force will be on duty over the weekend, along with hundreds of public works employes who handle tasks from the restriping of Pennsylvania Avenue to installing 72 parade-route toilets to welding shut more than 50 manholes that could provide refuge for attackers during Monday's procession.

The Army, the city and the Secret Service have completed plans to collaborate to seal off downtown early Monday with concrete barriers on the cross-streets along the parade route, and with red steel cables to keep back the crowds.

The inauguration crowds are a boon to scores of Washington-area restaurants and more than 50 hotels -- none closer to the action than the Hotel Washington at 15th Street and Pennsylvania Avenue NW, which has been hosting inaugural events since 1920. "It is festive, and it is hectic," said Muneer Deen, hotel general manager, who presided over a flurry of preparations by his 250-member staff and a contingent of 75 extra employes hired just for inaugural weekend.

The hotel lobby features a display of the menu for the 1933 Roosevelt-Garner inauguration, advertising the deluxe $1.50 dinner at the fashionable hotel that 52 years later features considerably costlier fare. Hotel Washington alone will host 22 parties Monday, many sponsored by large corporations such as Nabisco, Northern Gas Co., and The Washington Post.

With its rooftop vantage point of the White House and much of the parade route, the hotel, like most buildings nearby, will have a Secret Service presence, and will impose heavy security measures on guests, including strict instructions not to open windows or attempt to venture onto the upper terrace.

In addition to Secret Service scrutiny, all downtown hotels, motels and restaurants have been subjected to particularly rigorous health and safety inspections since December, said Ben Johnson, the D.C. business regulation administrator. "We are inspecting everything," he said, including all Inauguration Day vendors who will be scrutinized by a roving 14-person inspection staff.

The city's 6,000 licensed vendors will be vying for the choicest spots this weekend, although only 300 spots are available within the parade area, Johnson said. The committee has reserved 50 spots, and vendors selling inaugural items will compete for 250 other spots chosen by police department lottery.

Washington's 47th inauguration (three earlier ones were held in New York and Philadelphia before the capital moved here) will also be something of a coup for the D.C. Convention Center. The two-year-old center will host two inaugural balls and two major galas produced by Frank Sinatra, events that will make the center a showpiece for influential visitors and for a television audience that may reach 40 million, inaugural officials said.

But as the downtown center buzzed with activity and with the whine of power-drills and power-saws, the mood was surprisingly routine. "It is really just another convention. . . . We are prepared," said Michael Rogers, the deputy general manager, who helped coordinate plans for inaugural events that will fill four exhibition halls, 37 meeting rooms, and the entire 800,000-square-foot center.

The inaugural committee pays particular attention to what Henkel calls the "happiness factor" it hopes to provide for participants. Henkel instructs his operations team to ask, for every nuance of every inaugural event: "Does this meet the test of the happiness factor?"

This week, his team fanned out across the city, trying to make it all work. It was not an easy task.

Michael Lake, a committee "advance man," stood in subfreezing wind Wednesday at the Jefferson Memorial, site of Sunday's "Young Americans" pageant, waiting for an operations trailer to arrive. It didn't come. The driver had gotten lost.

Then he rushed to the Air and Space Museum, where crews were waiting to construct stages for one of the nine inaugural balls. Hundreds of feet of wood had been delivered for the job. But none of it had been fire-proofed, as the museum requires.

That problem landed on Henkel's desk a few hours later, along with an ultimatum from one orchestra, whose leader didn't like the Metroliner train accommodations his band had been handed. "They said if we didn't fly them down, they weren't coming," said Henkel. "I was sorely tempted to take the challenge, but I decided to pay the extra and fly them in from New York."

Henkel is working his way through a 40-page, hour-by-hour countdown list of things that must be done before the last inaugural waltz is danced sometime after midnight Monday. "Our mission in life is to solve problems," he said. "I'm confident we can satisfy that."