The weather forecaster, the National Park Service people and the man with the fireworks were holding their collective breath last night in hopes that the area's relentless rains will not wash out the annual Independence Day pyrotechnics scheduled on the Washington Monument grounds tonight.

Nearly two inches of rain have fallen since Sunday, and the National Weather service is calling for cloudy skies and a 40 percent chance of rain today and a 20 percent chance tonight.

"We've got our fingers crossed," said Sandra Alley, spokeswoman for the National Capital Region of the National Park Service, which is responsible for the site on the monument grounds where the fireworks are scheduled to be set off at 9:15 p.m.

"If we get rained out, it'll be the first time in 20 years," said George Zambeili, president of Zambelli Fireworks Co., of Now Castle, Pa., the man who has bought the Fourth of July fireworks here since 1959.

Whatever rain occurs today should taper off as evening approaches, said National Weather Service forecaster Charlie Chilton. "So the longer they wait (for the fireworks), the better their chances are of escaping the rain."

Meanwhile, the rain that has accumulated since Sunday has marred the long Independence Day weekend for travelers and beachgoers, caused flooding along the upper Potomac River, knocked out electric power in parts of Bethesda and created a general atmosphere of misery hearabouts.

A string of thunderstorms in West Virginia and Western Maryland Sunday triggered minor flooding on the Potomac River above Cumberland yesterday. At least 60 persons were evacuated from low lying homes in the town of Kitzmiller, Md.

Heavy rains in Southwest Virginia also caused flooding in the streets of-Wytheville. Lightning struck two houses, burning them to the ground, and one man died reportedly of a heart attack as he helped neighbors remove items from one of the burning houses.

Weather service river forecaster Leo Harrison warned that the Potomac River in the Washington area will reach a "hazardous stage" in the next day or two, which is well below flood stage but could be "very dangerous" for canoeists and fishermen. He said the river will not recede below the hazardous stage before Friday.

"We had five drownings on the river during Memorial Day weekend," Harrison said, "and we'd hate like hell to have any more."

Two areas of Bethesda lost electric power for brief periods early yesterday, when short circuits and other damage were caused by the rains, according to the Potomac Electric Power Co.

About 200 customers in the area near Bradley Boulevard and Redwood Avenue lost power from 5:45 a.m. to 8:19 a.m., Pepco representative Doris Newcomb said. In a separate blackout, about 100 homes near Selkirk Drive and Oakney Parkway were without power from 2:13 a.m. to 3:33 a.m.

With the rain since Sunday, the year's total so far comes to almost 23 inches, more than 4 inches above normal for the first six months of the year.

While creating floods, blackouts and general unpleasantness, however, the rain also has kept the area water table healthy and maintained a surplus in area rivers and reservoirs for the hot weeks ahead. At the same time last year, the area was beginning to suffer from a summer-long drought that caused mandatory water use restrictions in some parts of suburban Virginia.

As for the fireworks scheduled toningt, Zambelli says he can set off the roman candles, aerial explosives and other displays even if it is raining, "as long as it's not too dense." If the fireworks are rained out, the park service says it will reschedule them for tomorrow night.