Jason Bales handled the train ride like a young Casey Jones. In the stroller, he was Mario Andretti, ready for a spin around the track. And when he saw the carousel, there was rodeo in his eyes.

Alas, the bronco bustin' days of 18-month-old Jason were brief. The little wooden filly went up and down, up and down, and just about broke his heart. "Oh look," said mother Hope, watching Jason go around on the carousel, clinging to father Chris' arm. "He's starting to cry."

Such is the life of adventure, a little scary sometimes. But Jason survived his brush with the fast lane in what had been an otherwise beautiful day at Burke Lake Park in southeastern Fairfax County.

Like thousands of other Washington-are residents who came out of doors yesterday, he and his parents were pleasantly accommodated by something of a meteorological miracle: a summer day in Washington that didn't make you wish you were in Alaska.

Sometime Saturday night, according to National Weather Service forecaster Cliff Crowley, a weak high-pressure system snuck into Washington, bringing with it crystal blue skies, temperatures in the mid-80s and an unusually low humidity reading of 45 percent.

Unfortunately, that weak system didn't have much staying power, meaning the area is in for a gradual return of steamy weather, with humidity rising and temperatures climbing to the high 80s today and to 90 tomorrow.

But at least yesterday, by Washington standards, was just about perfect.

At Burke Lake, about 1,500 were on the golf links, at picnic tables, in row boats or just lying in the grass, taking advantage of the park's 880 tree-shaded acres and 218 acres of fish-stocked lake.

By mid-afternoon, nearly 300 golfers had signed in to smack balls around the park's 18-hole, par-three course. Scores had staked out positions at the park's 220 picnic tables. Frisbees flew in profusion.

"I bet everybody in Fairfax County is out here," said Dennis Ingelbretsen, an electrical engineer, who was teaching his sons Mark and Brent--5 and 8--how to sail a radio-controlled boat. "It's just beautiful recreation."

At the Burke Lake marina, dozens of people dressed in shorts and sneakers lounged on benches or fed the ducks while Ingelbretsen, who designs radio-controlled aircraft for a Defense Department contractor in Falls Church, maneuvered his 36-inch-long racing yacht, the Tidewaters.

Trimming the sails from shore with the aid of a transistorized radio control box, Ingelbretsen said, "It's got a five-pound weight in the keel, so it's practically impossible to tip it over."

Mark took the controls, let out the sails and tacked the Tidewater into the breeze. It heeled nicely to starboard and Ingelbretsen said, "We'll rent a boat and go chase it around now."

The Springfield United Methodist Church softball team, the Red Flames, was easing the pain of last week's loss in the county church league finals with steaks, hamburgers and beer. After a brilliant season and march to the championship, they said, they had choked in the last game against Mount Vernon United Methodist.

"We beat the Lutherans, the Baptists and the Presbyterians," said coach Len Murphy. "They [Mount Vernon] just outhit us."

So they had come to Burke Lake, 20 of them, to gear up for touch football in the park. "It's the nicest park around," said the team's shortstop Keith Krueger, 22. "A lot of nice girls."

"Keith," said outfielder Terry Clifford, "has bad taste."

At the train station, parents and children were lined up at the ticket window to pay 50 cents each for the 1.5-mile looping ride through a forest of oak, birch and elm. Greg Spinner, 23, who's been working at Burke Lake for the last six years and studies photography on the side, gave a long, shrill blast on the train whistle, rang the bell, and eased the locomotive's four-cylinder powerhouseinto gear.

The children squealed as the train lurched out of the station. Spinner eased back on the throttle to cross the first switch, then let her out again until he was cruising at about 15 miles per hour.

"In the spring, everybody is looking for the sun," he said. "They all head for the open areas. It looks like a beach. Today, there's more than usual for this time of year."

He turned to look at some of the smiling faces trailing in the passenger cars. "We get a lot of happy people here."