Californians should prepare for flooding and potential mudslides as «heavy or excessive rainfall» is expected over the weekend and into next week, forecasters warned early Saturday.

As recovery efforts continue in parts of the state that was battered by storms earlier this week, the National Weather Service said in a statement. bulletin that a pair of Pacific storm systems were forecast to impact into the west this weekend «bringing heavy rain at lower elevations, significant snow on the mountains and high winds.»

The first system would approach the coast on Saturday and move inland, the bulletin said, adding that there were «multiple slight risks of excessive rainfall,» which could lead to localized instances of «urban and small stream flooding, as well as like landslides.

“More moderate showers will continue through Sunday before a second storm system approaches the coast early Monday morning,” the bulletin said.

More than 15,000 people lost power early Saturday morning, according to

The Golden State has been battered by a series of storms since late December, killing at least 21 people, according to an NBC News tally.

Gov. Gavin Newsom and other state and federal officials pleaded with residents to «be vigilant» and avoid complacency as the latest weather systems approach.

“I know how fatigued everyone is,” Newsom said in a speech during a visit Friday to the coastal enclave of Montecito in Santa Barbara County that was evacuated earlier this week.

“Just keep a little more vigilance over the course of the next weekend,” he added.

His visit came on the fifth anniversary of the landslide that killed 23 people and destroyed more than 100 homes in the upscale community.

Thanking members of the California National Guard for cleaning up a sump that was built after the mudslide to divert rain, he asked people to use «common sense» and obey instructions from law enforcement officials.

Nancy Ward, director of the California Governor’s Office of Emergency Services, echoed Newsom’s message and urged people to be cautious.

“People will become complacent, but the ground is saturated. It is extremely, extremely dangerous,» Ward told a news conference. «And that water can continue to rise long after the storms have passed.»

Damage assessments from the recent storms, which have already begun, are expected to exceed $1 billion after roofs were blown off homes, cars were submerged and trees were uprooted in parts of the state.

In southern California, authorities determined that a storm-related sewage spill into the Ventura River was much larger than initially thought. Two Ojai Valley Sanitation District sewer lines damaged on Jan. 9 spilled more than 14 million gallons, the Ventura County Division of Environmental Health said Thursday. Warning signs have been posted along the river and beaches.

Elsewhere, residents tried to salvage their belongings and rescue teams pulled survivors from under collapsed homes Friday after a storm system spawned tornadoes and killed at least nine people as it tore through parts of Georgia and Alabama.

The widespread destruction became visible a day after violent storms tossed mobile homes into the air, hurled uprooted trees at buildings, snapped trees and utility poles and derailed a freight train.

Associated Press contributed.