Many Washington service station operators said yesterday they have yet to receive fresh supplies of gasoline for July, raising the possibility of tight supplies today and tomorrow and a virtually gasless Fourth of July.

"As far as the July allocation is concerned, nobody has told me anything," said Parker Gulf on South Capitol Street. "The dealers are operating in the blind."

Grady Sweeney of Kenwood Mobil in Bethesda said the company has informed him he may not receive any new gasoline until Thursday. If that happens, Sweeney said, he may have to shut down sometime today and stay closed through the holiday.

"I suspect a lot of stations will pump whatever they have left on Monday and Tuesday and may not have gas to sell on Wednesday," said Stephen Hannestad, deputy director of emergency preparedness for Prince George's Country. "My suggestion would be for people to get their gas before then."

Local officials and service station operators said yesterday they expected many area stations to open early today. But they were uncertain how long the stations would remain open in the face of intense demand.

Whether or not expected deliveries arrive today, indications were that today and tomorrow would be difficult for motorist seeking gasoline immediately after a weekend and just before a major holiday.

Officials and station operators said that the situation on the Fourth could be as bad or even worse than yesterday, when motorists spent up to two hours - and in a few cases much longer - waiting for gasoline, despite steps by the District of Columbia and Maryland to allocate reserve supplies to stations that agreed to open.

There were these related developments as the gasoline crisis entered the month of July:

Attendance both at local tourist spots and out-of-town resorts and theme parks dropped at least 10 percent this weekend, despite the beginning of what is traditionally the busiest week of summer. Police also reported traffic down about 10 percent at the area's major bridge and tunnel crossings.

The District of Columbia's energy units distributed 80,000 gallons to 10 stations to ensure they will be open the morning of the Fourth. But Maryland and Virginia officials said they have taken no specific steps to allocate holiday supplies in those states.

Beginning today, area service stations have been asked to display special flags indicating the available of gasoline. A green flag will mean both leaded and unleaded gasoline are available, yellow signifies only leaded can be purchased, while red means the pumps are closed.

The area-wide system of odd-even gasoline sales resumes today after being suspended, as usual, for the weekend. Under the system, motorists with even-numbered license plates can buy gasoline today and other even-numbered days; similarly, motorists with odd-numbered plates can buy gasoline tomorrow and other odd-numbered days.

Wednesday, the Fourth of July, is a federal, state and local government holiday and the odd-even rules will be suspended.

Lines that stretched a mile or longer at many stations started forming as early as 5 a.m. at the three dozen or so stations that were open yesterday in the District and suburban Maryland and Virgnia. Virtually all stations had sold but their daily allocation or run dry by early afternoon.

Dr. Linda Rock, a D.C. General Hospital Physician, said she joined the line at Stevens Exxon at Georgia and Missouri Avenues at 5:30 a.m. She waited until 10:15 for gasoline in a line that snaked around street corners and through alleys for more than half a dozen city blocks.

"When I closed last night a camper showed up to wait in line," said Bill Kistner, manager of Hampton Mall Exxon in Capitol Heights. "He was still there when I opened today."

Kistner and many other operators in Maryland said they would not have opened yesterday had they not received "setaside" allocations from the state. Kistner received 4,000 gallons, which he had sold by mid-day yesterday. Altogether, about 26 stations in suburban Maryland and D.C. were able to stay open yesterday because they had received allocations.

"We opened at around 8 o'clock, pumped our 4,000 gallons, and shut down just before noon," said James Herring, owner of Germantown Gulf, where motorists waited up to two hours for gasoline.

The area's three emergency gasoline hotlines -- operated by the District, Prince George's Country and the American Automobile Association -- were in constant use yesterday morning. But by noon, only the Prince George's line was still attempting to locate open stations.

"We've got four lines here and as soon as one is hung up, it's ringing again," said Stephen Hannestad.

All three lines will be in operation this week, according to officials. Drivers in Northern Virginia are urged to call their local governments or police for information about gasoline availability there.

Crown Oil Company's 13 Washington-area stations all opened for business yesterday at 7 a.m. and pumped gasoline for about six hours until their daily allocations of about 7,500 gallons ran out, according to district manager Joseph Gilboy. He said the stations would open every day this week, including the Fourth.

Other station operators were less certain. "They deliver gas to me when they feel like it," said Gulf's Henry Parker. "When I called and asked why my gas wasn't on time,, they [Gulf's Fairfax supply dispatcher] hung up on me."

Officials at the Cheaspeake Bay Bridge and Baltimore Harbor Tunnel reproted about 10 percent fewer cars per hour than on a normal summer Sunday.Spokemen at King's Dominion amusement park and Williamsburg reported fewer tourists but gave no figures.

Ocean City police reported slightly smaller crowds than last year but also gave no figures. At Virginia Beach, hotels and motels reported 60 to 80 percents occupancy instead of the 90 to 95 percent levels expected during the week of the Fourth.

"You can look out at Atlantic Avenue and see that the season has never arrived, said Sylvia Greenspoon, owner of Ocean Ranch Motel at Virginia Beach.

Hotel occupancy in the Washington area remained high, but there were indications that tourism here also is slipping. The Smithsonian's seven Mall museums had 600,000 fewer visitors in the last two months than during the same period in 1978. Attendance at the Smithsonian's star attraction, the National Air and Space Museum, was down 21 percent last month compared to June, 1978.

Despite yesterday's long lines, tempers remained calm for the most part and few incidents were reported. An attendant at the Shell station at the corner of West Glebe Road and Mount Vernon Avenue in Alexandria was treated and released at Alexandria Hospital for a facial cut he received during a scuffle with a customer he apparently accused of cutting in line. As of last night, police said no charges had been filed. They declined to release the names of either party.

An off-duty D.C. policeman who tried to cut in line at Sevens Exxon in the District was turned away after complaints from irate motorists behind him. CAPTION: Picture, The line of cars was already more than a block long at 7 a.m. Sunday as motorists waited for the Colonial Exxon station, at 3327 M St. NW, to open, By James A. Parcell -- The Washington Post