An almost perfect late-summer day smiled on festivities of every sort in the Washington area yesterday, from an ancient Hindu festival to that modern good-time classic, a river raft race.

More than 7,000 people, according to Park Police estimates, crowded in or around the Potomac River for the fifth annual "Rambling Raft Race," an aquatic free-for-all sponspored by WPGC-FM radio and Budweiser Light beer.

Down the Chesapeake Bay, hundreds of sailors participated in the Governor's Cup yacht race, sponsored by the St. Mary's College Foundation, St. Mary's City, Md. More than 1,000 persons watched 300 boats finish the race, which 307 boats began in Annapolis Friday.

Gov. Harry Hughes presented trophies to the winners of the race, the largest regatta on the bay. There was no overall winner chosen, race officials said.

Meanwhile on the Mall, India's oldest Hindu festival was reenacted for the first time here yesterday afternoon as three blazingly colorful, 50-foot-high chariots rolled along in a holy parade.

Pulled for two hours by followers of the American-based International Society for Krishna Consciousness who chanted, sang and danced in jubilant celebration along the way, the chariots resembled exotic parade floats.

According to tradition, the wagon-wheel vessels represent the chariots used on a sacred journey embarked upon thousands of years ago by the god Krishna, his brother, Balarama, and sister, Subhadra. Officially, the day was christened "Ratha-yatra Day," literally, chariot parade.

The festival's participants, clad in saffron and white robes with their heads shaved except for bunny rabbit-like tufts in the back, jumped and raised their hands skyward, clanged bells, beat drums and repeatedly chanted "Hare Krishna."

The chant became a melodic nursery rhyme as dozens of children riding in an oxen-drawn cart yelled: "Hare Krisha! Hare Bol! Hare Krishna! Hare Bol!" which means, according to Swami Sesa Das, "Please chant the holy names of Krishna."

Taking a pause from the commotion of the parade, several Krishna followers knelt and meekly bowed to the ground in front of Swami Satsvarupa Goswami, one of 13 gurus in the International Society for Krishna Consciousness, who was at the festival yesterday to deliver a message.

"The purpose of this festival is to promote the consciousness of God and to expose people to it," he said. "Our movement is cultural and philosophical. It's a very blissful experience to chant the names of God."

At afternoon's end a storm swept up the river, overturning some light craft and at least temporarily dampening the festivities on the Mall. No serious injuries were reported.

Although precise figures were not available, an officer in the D.C. police harbor unit estimated that a "whole bunch" of small boats capsized on and near the Potomac River during the brief but furious storm, necessitating a number of rescues. No injuries were reported. Many of the boats were in the area of the Naval Research Laboratory when the storm struck, police said.

In addition, winds and lightning caused a scattering of electric power outages across the area. About 3,500 homes in various sections of Northern Virginia, including parts of Falls Church and the Merrifield area of Fairfax County, lost power at some point, according to an estimate made by a spokesman for the Virginia Electric and Power Co.

A spokeswoman for the Potomac Electric Power Co. said the most severe problem in the District and Maryland was a damaged feeder line that cut off power to about 700 homes in the Fort Washington area of Prince George's County. By 9 p.m., about four hours after the storm, almost all service had been restored, according to the utilities.