A second round of rain from a rare spring storm swept into drought-stricken Southern California on Friday, along with heavy winds, snow in the mountains and the possibility of hail and lightning.

Scattered thunderstorms were expected from San Diego north to Ventura County as the brunt of the system moved on shore and headed east, the National Weather Service said.

Drivers were urged to use caution on roads in the San Bernardino and San Gabriel mountains, where between 3 to 6 inches of snow was possible above 6,000 feet. Temperatures hovered around freezing at higher elevations.

In Arizona, crews were plowing highways in the Flagstaff and Williams after snow fell across the northern part of the state. The National Weather Service said over 7 inches fell at its office in Bellemont west of Flagstaff and more was expected.

The cold storm from the Gulf of Alaska brought bands of brief, heavy downpours Thursday to Los Angeles County and points east and south, dumping anywhere from trace amounts in some places to up to 1 ½ inches in portions of San Diego and Ventura counties.

Firefighters rescued six motorists and a dog who became trapped in 3 feet of water on a San Diego street, and they pulled a man from the rushing water of a flood control channel in Northridge, about 25 miles north of Los Angeles, authorities said.

"One minute it's a little bit of water and all of a sudden it got deeper and deeper really fast," Capt. Joe Amador of the San Diego Fire-Rescue Department said about the flooded street.

The rain was doing little to ease water woes in the historically parched state.

"Any kind of rain, like we had last night, is certainly welcome. Anything wet is welcome," said climatologist Bill Patzert of NASA's Jet Propulsion Lab. "But it's not getting us out of the drought."

Flooding and debris flows are possible if thunderstorms form over foothill areas stripped bare by wildfires.

The downpour caused rare rain delays at the San Diego Padres' game against the Washington Nationals at Petco Park and the Los Angeles Dodgers' game against the Colorado Rockies at Dodgers Stadium. Meanwhile, snow in the forecast for Friday forced organizers to relocate the Amgen Tour of California bicycle race from Big Bear Lake in the San Bernardino Mountains to Santa Clarita.

It also soaked the Hollywood Walk of Fame, where flowers were being laid on the star of blues legend B.B. King a day after his death.

An outdoor commencement ceremony at University of Southern California went on despite the wet weather, with attendees told to leave their umbrellas behind. Many people, including graduates, wore crimson and gold Trojan ponchos.

The drenching was a bit of a surprise to forecasters.

"We don't see these kinds of storms this late in May," Stuart Seto with the National Weather Service in Oxnard said, "and not this cold."

The rain was met with joy by parched residents.

"I've been actually waiting for this like, a whole week, for thunderstorms and rain and everything," Michael Karapetyan of Glendale told KABC-TV. "I'm tired of this sunshine and sunshine."

To the north, the storm brought thunder and lightning to the San Francisco Bay area with some bolts reaching the ground. Brief spurts of rain and hail were reported but generally only in trace amounts. Some street flooding occurred in Fresno.