On one of Washington's glorous autumn days, the Smithsonian's Festival of American Folklife opened yesterday on the monument grounds to run through the Columbus Day weekend.

It was a day - bright, brisk, ripe with harvest reapings - that served to vindicate in those pushing to hold the festival in October instead of July's heat and humidity.

And it still was a gorious day despite the fact that Ella Noris, the 85-year-old salmon roaster from California, didn't have the right knife, fish, or wood and Phipps Bourne, the bearded blacksmith, had no coal for his fire.

"If it had rained today, I never would have been heard from" said Charles Blitzer, the Smithsonian's Assistant secretary for history and art.

As for Ella Noris, she was happy with a new set of knives with straight edges and the promise of some West Coast salmon to be flown in.

"I want the great big fish from Trinity River," she explained, poking at the fire of Pennsylvania birch wood, tolerable as a substitute for the alder wood that her Yurok Indian tribesmen use because it does not flavor the fish.

Joan Mondale, a potter and craftsman herself, opened the 11th annual Folklife Festival, held near 14th Street and Constitution Avenue, yesterday and had to be reminded often of her schedule as she obviously relished the music, crafts and food.

At one point, Ray Melton of Woodlawn, Va., serenaded the Vice President's wife on a lap-held dulcimer.

"Was that "Red River Valley?" Melton was asked.

"That or 'Can I Sleep in Your Barn,'" Melton said without a trace of a smile.

About the only person who didn't seem to be enjoying himself yesterday was a Secret Service agent who looked positively miserable as Mrs. Mondale passed the wheat threshing exhibit area.

"Oh, what this does for my hay fever," he explained to the accompaniment of a series of sneezes.

This opens the second decade of the Smithsonian's folklife festival. For the first time, it's being held in the autumn. And this year there is closer emphasis on trying the program to Smithsonian's rich museum exhibits and research.

After the big Bicentennial bash that ran almost 12 weeks last year, this year's festival is much more manageable and absorbable.

This year, at harvest time, there are hayrides and wheat threshing demonstrations, sausage-stuffing, cornmeal milling, apple-butter boiling and clam bakes.

"That's if the coal ever arrives for the threshing machines," said Bourne, the blacksmith, who is also waiting for coal.

Bourne, whose sentences twang with Southern Virginia overlay, explained that he does demonstrations as well as actual horseshoeing.

"Some of those horses get dangerous," he observed. "Some can kick high enough to get a few birds before they come down."

The festival has special programs for Virginia's music and crafts, including a gravedigger-blues singer from Fairfax.

And some of the visitors to the festival will be providing folklore themselves. When they visit the Smithsonian's "Nations of Nations" exhibit, they will be asked about memories and reminiscences prompted by the exhibits on old entertainers, sports heroes, schoolrooms. World War II barracks and the like.

It wasn't just the weather that prompted a shift in the folk festival date from July to October this year. Wilcomb E. Washburn, director of the Smithsonian's Office of American and Folklife Studies, emphasized.

"At this time we can better connect to both museums and the schools," he pointed out. "The outdoor exhibits can be integrated into the museum displays."

"That's one reason the festival this year is being held on the monument grounds area just across the street from the Museum of History and Technology. The Renwick Museum and the Museum of Natural History also are being used for demonstrations of ethnic cooking crafts and for music performances.

For visitors to the festival's outdoor exhibits, there will be daily programs with ballads, stories songs, gospel harmony, old-time string hands, hill-billy blues, and even spoon players.

For her visit to the festival yesterday, Joan Mondale was handsomely and appropriately outfitted in vest, ankle-high skirt, shawl turtleneck sweater and boots. The skirt material may have looked like an old quilt pattern, but it was a designer outfit created by Beth Oxberry of Daj, Inc., Minneapolis.

Mrs. Mondale spent time chatting with the apple-butter makers and cider pressmen but she also gave attention to special exhibits in the section of "America's Appetite for Energy."

There was the exhibitor pushing deboned meat (which saves energy because it takes less refrigerated space to store and less time to cook). Another booth featured solar ovens, which use shiny reflecting wings. A thermomenter showed the temperature at 220 degrees, which means you have to like your meat very rare or start preparing dinner in the morning.