NAPA, Calif. (AP) - A powerful storm sent rivers and creeks over their banks and into cities and set off mudslides that blocked major highways across Northern California on Saturday. At least a dozen people had to be rescued from the rushing water, and forecasters were warning of another storm on Sunday.

California officials urged residents along the Napa and Russian rivers and on hillsides to collect their valuables, gather emergency supplies and get out.

In the city of Napa, near the heart of wine country, the river rose 5 feet over flood stage as water surged into downtown before beginning to recede. Napa officials estimated about 1,000 homes flooded.

"We had so much water in such a short amount of time that man hole covers were popping all over the city," said Napa City Councilman James Krider.

The Russian River was menacing the Sonoma County town of Guerneville, where forecasters warned that the river was still rising and could reach 14 feet above flood stage, and officials were urging residents to evacuate.

Farther inland, Reno, Nev., was seeing its worst flooding since New Year's Day 1997, when high water caused $1 billion in damage. The Truckee River swamped downtown buildings on Saturday, and parts of nearby Sparks were under 4 feet of water. Many businesses along the river closed and owners spent the day piling sandbags.

Rescue crews also had their hands full, plucking stranded drivers from cars and flooded homes across the region.

In Sonoma County alone, helicopters were used in six rescues, and firefighters rescued two more people from a mobile home park, where 4 feet of rushing water washed at least one home off its foundation.

"We are just very strongly recommending that people living in the lower areas lock up everything and go to higher ground," said Linda Eubanks of Sonoma County's Office of Emergency Services. "Just because it stopped raining doesn't mean the water is going down."

Rick Diaz took off on his own through a flooded Petaluma neighborhood in a 14-foot Zodiac boat, ferrying residents to dry ground and rescuing their pets.

"He's a hero," said a tearful Suzi Keber after the wetsuit-clad Diaz rescued two pet lizards from her home.

In downtown San Anselmo, the creek overflowed into as many as 70 businesses, said town administrator Debbie Stutsman. Two people rescued from the rising water there were hospitalized with hypothermia, she said.

"I'm looking out of my office now at merchants bringing their damaged goods out into the street," Stutsman said. "The entire downtown area was under 4 1/2 feet of water."

"It's pretty bad all across town," she said.

Mudslides closed several major roads, including Interstate 80 in the Sierra Nevada about 25 miles west of Reno. Six tractor-trailer rigs were caught up in one slide on the interstate early Saturday, but no injuries were reported.

I-80, the major corridor linking Northern California and points east, was expected to remain closed for at least two days, said California Department of Transportation spokesman Mark Dinger.

"No work can be done until the slide stabilizes and we don't know when that will occur," Dinger said.

Together, the two weekend storms could add as much as 6 inches of rain to the already water-logged region, said Rick Canepa, a weather service meteorologist in Monterey. More than 2 feet of snow was also forecast in the Sierra Nevada.

One woman suffered a broken leg when a mudslide destroyed her home in Santa Rosa late Friday. It took firefighters nearly an hour to free her from the mud and debris, said Santa Rosa Fire Battalion Chief Andy Pforsich.

Flash flooding and landslides temporarily closed Interstate 5 both ways near the Oregon line. U.S. Highway 101 was closed by fallen trees and mud south of Crescent City.

Rain also started moving into Southern California on Saturday, and flash flood watches were issued for areas scarred by wildfire in Santa Barbara, Ventura and Los Angeles counties.

Even Pasadena's Rose Parade was in danger of rain on Monday. The parade has had dry days for half a century, but float builders were still prepared to roll out sheets of clear plastic to protect delicate flowers.

"I'd hate to be selfish to ask God just for this favor, but I came far to help decorate and see the parade for the first time," said Jean Steadman, 79, of Georgetown, Texas, as she gathered yellow roses for a safari-themed float.