AT NINE O'CLOCK it was uncertain whether the prize for pyrotechnics belonged to Mother Nature or to Boom-Boom Zambelli. The thunderstorms were unexpected: hazy, hot and humid, mid-90s, said the weatherman. But the thunder and lightning formed a dramatic counterpoint to the guns of the "1812 Overture" and the magic explosions wrought by the fireworks king. And the rain, instead of ruining the festivities, seemed to unify the crowd and fortify everyone's determination to have a good time.

Among the standouts at Monday's celebration were the paraders, who were decked out in everything from full Indian regalia to long-sleeved worsted band uniforms. They bore the brunt of Washington's Amazonian weather and marched through heat, humidity and electrical storm. Their music and their spirit got the day off to just the right kind of start. And let's hear a good word for Wayne Newton. As the man in the middle of the James Watt-Beach Boys brouhaha, he was subjected to a lot of unnecessary ridicule, all of which he handled like a gentleman. The man came to our town with a full orchestra and crew and gave a free show and a good time to some 225,000 people.

There were other stars Monday night--Willie Stargell reading "The Lincoln Portrait," the indomitable Leontyne Price filling the air with Puccini--but we confess that our favorite was a man who is relatively new to Fourth of July celebrations but who seems to have captured the spirit of the occasion admirably. Mstislav Rostropovich, conductor of the National Symphony Orchestra, and late of Moscow, U.S.S.R., not only led his musicians in the "Stars and Stripes Forever" with gusto but also took off his shirt, rolled up his pants and joined the rain-soaked audience in an impromptu conga line. What a gesture; what a sight!

At the end of the evening the good will continued. Metro ran smoothly and at holiday prices. The crowds were orderly, and very few arrests were made. The Park Service reports that citizens organized to clean up litter, as they had done throughout the weekend. It would be only natural if those of us who live in this city took its beauty and its vitality for granted. But a few times a year an evening drive past the monuments or a glimpse of the Capitol on a cloudless day touches even the most jaded among us. Monday was such an occasion, reaffirming for us the belief that Washington is the best place in the country to celebrate the Fourth of July.