The halls of Congress are empty except for the echoing voices of tourists; the City Council chambers in the District Building are deserted; the President and the police chief have spent part of the month out of town on vacation, and the major is taking a few days of vacation.

"Washington must be on vacation - either that or what they say at home about government people in Washington never doing anything is true," said Cheryl DuVal, a visitor from Kansas City, Mo.

"Just look, she said, moving from one hand to the other her canvas handbag with the bright blue monogram of the Capitol dome. With her free hand, she motioned toward a maze of empty offices and a few idling workers in the Department of Housing, Education and Welfare where she was visiting a friend this week.

"Everyone drops down a couple of gears in August," said her friend, who Washington takes a break from work did not want his name or his department identified in a story about how during August.

"The Congress is gone, supervisors are on vacation," he said. "Sen. so-and-so's aide isn't calling with a request for something. Besides, it is too hot to be in Washington during August "if you've got the money and the vacation time."

Throughout Washington, steamy summer weather and August vacations have put the city in hot, syrupy slow motion.

Washington correspondents, lawyers and schoolboys all seem to be out of town on a summer lark or taking long lunch breaks, long weekends and leaving the office early.

Monuments, government buildings, honking snarls of cars at traffic circles and flashing time-and-temperature signs outside banks - all seem to have been left to persons who could not wait until August for a vacation or who are waiting for a cool weather getaway.

A random check government offices recently found that persons temporarily in charge thought that about 25-30 per cent of their work force "and that includes a lot of administrators, the bosses," as one woman at the Commerce Department said - were on vacation last week.

City officials estimate that 25 per cent of the city's police and firefighters are on vacation. The city and federal government and private businessess all seem to be operating with skeleton staffs.

In D.C. Superior Court, the only cases scheduled for trial in August involve long arguments and paperwork. During July and August, casses involving contracts and debts are not scheduled because about one-fourth of the judges usually are on vacation. Eleven of the 42 judges were vacationing last week.

Washington travel agents agree that August is "the month when local residents take vacations.

"We're not so busy now because we were planning for these trips in June and July," an agent at Rogers Travel Agency said.

At Thomas Cook, Accent Travel and Admiral Travel, agents all agreed that last week may have been the year's busiest for vacations.

"We're made travel plans for a huge number of people, especially government people. They don't feel they are going to miss anything too important because they know everybody else takes time off in August, too," said Phyllis Brill, owner of Accent Travel.

Dick Olson, special assistant to House Majority Leader James C. Wright Jr. (D-Tex.), said almost all House and Senate members are out of town for "district work sessions," or what formerly was called the August recess.

Olson said Wright's executive assistant, Craig Raupe, is not on vacation but, like many such congressional aides, is working on "banker's hours" instead of his usual 7:30 a.m. to 7:30 p.m. schedule.

The House restaurant is closed during August, the Senate dining room is not, Olson said.

"You just don't feel the same pressure (now) to get back after lunch," said Olson, who is going on vacation next week.

President Carter has been out of town for most of August. He went home to Plains, Ga., the first week of the month and has been at Camp David recently.

The vacationing White House has been twitted recently by comic strip author Gary Trudeau. In a recent Doonesbury strip, Trudeau pictured the Isaeli prime minister calling the White House to announce a military attack in the Middle East only to have to leave a message with a White House switchboard operator who asked him to repeat his name.

On 14th Street NW above the District Building and the downtown shopping area, where one store owner noted that mid-August always is "deadly" for business, strip joins are in a late-summer slump.

"They'll come in and get a beer, but it ain't like the winter. They can walk around the (Thomas) circle and see a lot more girls than they can in here," said a bartender at the Butterfly Night Club, 823 14th St. NW.

On Vermont Avenue and 14th Street NW, from K Street to Thomas Circle, no one appears to be vacationing. A women walks and waits for a swarm of men sauntering along hot streets in search of excitement. Occasionally, one woman strolls to curbside to bend over and discuss business through a car window.

"Vacation! Honey, are you crazy? With all these people out here? Besides, I haven't even decided where I'm going (on vacation)," said a blonde woman perched atop stacked, white-heeled shoes. A round of giggles from women nearby followed her remarks.

Farther up 14th Street near T Street NW, an area reputed to be one where drug selling proliferates, the sidewalks are packed with persons loitering in front of bars and fast-food shops.

"These are street people, and this is their favorite time of year to be on the street. These folks don't have a summer place in the country or air conditioning," said a D.C. policeman, looking at the scene indifferently from his cruiser.

In Georgetown, discotheques were doing business as usual but with fewer dancers. A waitress waiting for an order of drinks at Tramps said one Friday night crowd was not the same crowd that patronizes the club at other times of the year.

"It is a lot younger crowd, a lot of tourists and kids who are working here for the summer," the waitress said.

"The real Washington night club set make sure they know someone with a beach place," she said. "You know it's not classy to disco on a Friday night in August."