With the din of firecrackers and the dancing of lions and dragons, Washington's Chinatown gave a rousing welcome to a new year yesterday.

As the afternoon temperature reached a record 78 degrees, revelers in T-shirts, blouses and shorts thronged to H Street NW. Dancers in bright costumes weaved and leaped to celebrate 4683, the Year of the Ox, which started Wednesday, according to the Chinese lunar calendar.

D.C. police estimated a crowd of 4,000. Organizers of the event said there were about 10,000. Both agreed it was the largest turnout in years for the celebration, which is usually attended by people in overcoats and gloves.

After a 40-foot string of firecrackers was set off from a construction crane, groups of lion dancers, accompanied by drummers, pranced from restaurant to restaurant along the 600 and 700 blocks of H Street and nearby Seventh and Eye streets. At each stop there were more firecrackers and more dancing. The performers were rewarded with red envelopes of "lucky money," usually a $10 or $20 bill.

"The Chinese people work hard," said Daniel JoJo Yuen, 19, of Seabrook, Md., who said he holds jobs in an electronics assembly plant and a Chinese restaurant. "They come down here to celebrate and to make noise to scare away the evil spirits."

Non-Chinese made up most of the crowd, and some of those expecting a western-style parade seemed disappointed.

There was one marching band -- from McKinley High School in Northeast Washington, one troop of scouts -- Brownies from Fairfax who carried paper lanterns, three groups from kung fu schools that teach Chinese martial arts, five lions composed of two dancers apiece, a group of waving dignitaries from Chinese community organizations and a long yellow dragon carried by 14 men who followed a dancer bearing a symbolic pearl, weaving and undulating in intricate patterns.

The procession took just 10 minutes to pass. However, most came by twice as they marched up H Street from Sixth Street to Eighth and then retraced their steps.

"I think I've seen enough," said Charles Maier, of Centreville, Md., as the procession started to pass for a second time. "We didn't have anything to do on the Eastern Shore today, but we're going to have to go someplace else to get some activity."

Kay Janda, of Sterling, said the dragon "looks like a big worm to me." But Tia Pickeral, 3, of Oxon Hill, said it "looked so nasty and so real." She had a good view, too, from the shoulders of her father, Ronald Pickeral, who is 6 feet 8 inches tall.

Hundreds of children watched from paternal shoulders and then covered their ears as the firecrackers boomed. Many of the lion dancers and their retinues came prepared for the noise, wearing yellow earplugs.

After the parade, leaders of the Chinese Consolidated Benevolent Association, an amalgam of 21 Chinatown groups that sponsored the event, read messages to the crowd from President Reagan and D.C. Mayor Marion Barry. Anna Chennault, a prominent supporter of the Chinese Nationalist government of Taiwan, brought greetings from Chiang Ching-kuo, the Nationalist president. Many buildings and spectators carried Nationalist flags.

There were no signs of the Communists who have controlled mainland China for 35 years and plan to pay half the $1 million cost of an ornate archway to be erected by the D.C. government in the middle of Chinatown, despite opposition from the benevolent association.

"Most of the people here are loyal to the old Nationalist government," said the Rev. Barnabas Cheung, chairman of association's program committee. "They suffered under the Communists, and they are unforgiving. For the next generation things may be different, but not now."