Rain Dampens the Mood : Weather: Showers disrupt high school graduations and traffic throughout the county. The late spring storm is expected to give way to partly cloudy skies today, and the weekend should be sunny.

An abrupt storm swept across Orange County on Thursday, dousing high school graduations and causing traffic wrecks and road closures as drivers clung to old driving habits.

“People drive by time, not by condition,” said Cypress Police Sgt. Ray Peterson. Several crashes, none serious, occurred outside Cypress High School as a crowd of 600 left soggy graduation ceremonies Thursday evening, he said.

The storm was expected to clear by today, forecasters said.

“Now I’ve uncovered the secret as to why those silly mortarboard hats are shaped that way,” said Tustin Police Lt. Christine George, whose city hosted two wet high school commencements and a flurry of fender-benders due to people “driving in their crazy way.”

In Newport Beach, a car skidded off the back bay bridge on Jamboree Road and wound up teetering over the open space that separates the southbound and northbound lanes, police said. No one was injured, but the accident caused some heavy delays on southbound Jamboree Road.

An injury accident closed the Corona del Mar Freeway in both directions near Jamboree Road for several hours Thursday evening, but by 8 p.m. traffic was running smoothly, a California Highway Patrol spokeswoman said. The extent of the injuries was unclear late Thursday.

“The phones were ringing nonstop for four hours,” she said. “We had a lot of minor crashes.”

The cold weather should end today, said meteorologist Steve Maneikis of WeatherData Inc., which provides forecasts for The Times. Partly cloudy skies today will begin to clear by the weekend as temperatures return to their normal mid-70s inland and high 60s along the coast, Maneikis said.

The late spring storm came from heavy rains and thunderstorms in the Gulf of Alaska. A strong Pacific jet stream whipped down the coast, bringing hail and heavy rains to the San Joaquin Valley and Fresno areas, Maneikis said.

“This . . . allowed the storm to maintain its strength as it pushed its way down to Los Angeles, causing rains and cold temperatures in Orange County,” Maneikis said. The high Thursday was only 71.

By 5:30 p.m., the southward-moving storm was causing gutters to overflow around the Santa Ana Civic Center, slicking roads and turning long-planned graduation ceremonies into muddy disappointments.

At Villa Park High School’s graduation in Orange, sporadic bursts of rain punctuated the ceremony.

“You will remember this graduation,” Principal Daniel Burch told the graduates and about 800 guests.

The commencement, planned to last two hours, was abbreviated to 45 minutes.

While the school band rushed through the National Anthem, a trail of 320 graduates tiptoed through the muddy Kelly Stadium with their arms held out from their sides to avoid touching their drenched blue robes. Names were immediately called out, eliminating speeches and awards.

Burch announced that the planned speeches would be mailed to the students and their families. The crowd sighed in relief.

After jumping over puddles to find a dry seat, Joseph Fran quickly gave up and hurried out of the stadium.

“At least we made our presence,” said Fran, who caught only a glimpse of his nephew.

Others stuck it out, hugging blankets or draping themselves with bath towels or plastic trash bags.

In Westminster, about 6,000 people attended a wet high school graduation. Police Sgt. Bill Lewis said, “Hopefully, the kids won’t go out and party too hard and be sliding around in this rain.”

Orange and Fullerton police each reported three rain-related accidents and three soggy graduations. In Costa Mesa, a traffic signal went out at Harbor Boulevard and Adams Avenue, tying up traffic, police said.