jrodriguez@mercurynews.com

SAN JOSE -- Autumn arrived Sunday afternoon with a splash of sunshine, as if it were a day stolen from summer and from all those sidewalk chalk artists, wine and cheese aficionados, and puppy lovers who got shocked Saturday by an early, sudden, drenching rain.

"Someone has been (rain) dancing!" That's what Katrina Marie Loera posted online after a cold front from Alaska swept through the Bay Area on Saturday -- the last full day of summer -- and literally washed away dozens of sidewalk paintings at the Luna Park Chalk Art Festival in San Jose. Despite the presence of colorful Aztec dancers, the festival organizers couldn't pin the gushing washout on Tlaloc the rain god.

"This was nothing unusual," said Diana Henderson, a forecaster with the National Weather Service in Monterey. "We just had a little, juicy cold front that came in and it had enough oomph to get through with some rain."

Well, tell that to the pups after their annual Bark in the Park festival in San Jose was canceled. And over at the Walnut Festival in Walnut Creek and the Lafayette Art and Wine Festival, they were running for shelter with glasses of chardonnay in hand.

Actually, Mother Nature and human customs don't always play by the neat, astronomical demarcations for the seasons.

The sun's track was directly above the equator on Sunday when, at exactly 1:44 p.m., it reached the celestial intersection called the autumnal equinox, when day and night are equal in time. The event signals the start of fall. For the next three months, the days will get shorter and the nights longer.

Even so, the signs of autumn have been around us since late August, when schools opened for fall terms, vineyards started harvesting their grapes and liquidambar trees started dropping their leaves and those dastardly, pointy seed pods.

In another jab at the autumnal equinox, the Winchester Mystery House in San Jose built a massive maze made of 5,000 bales of hay. Standing 7- to 12-feet tall, the maze opened on Labor Day, three weeks before the start of fall, the season of scarecrows and magic brooms made of straw. If football can start in late summer and still call itself an autumn sport, why can't a maze make the same hay?

Ed and Elaine Kwan, of Saratoga, brought their young daughter, Esther, who romped through the castle-like maze with her friend, Ella Langrock, for 25 minutes. The giggling tykes ran with abandon declaring at every dead end, "This goes nowhere!" But the girls found the way out once they put their minds to it. Ed Kwan, elated and somewhat pooped, asked them, "It's a-mazing, isn't it?"

Amazing still is the pleasant late summer and early autumn weather that marks the Mediterranean climate of the Bay Area. Forecaster Henderson said cooler but dry air will hang around in the storm's wake but things will warm again next by weekend, with mostly clear skies and highs in the mid-60s to mid-70s -- not too bad for the remaining outdoor festivals.

Contact Joe Rodriguez at 408-920-5767 and follow him at Twitter.com/JoeRodMercury.