Californians warned of 'disastrous flooding' as eighth storm barrels in

Disastrous flooding could hit parts of California this weekend, forecasters warned, as the eighth storm in succession barrelled in, with already water-logged land unable to soak up any more rain.

The most populous US state has been pummelled by near-record rainfall over a very wet three weeks that have already caused flooding, landslides and widespread power outages.

On Friday, yet another system threatened the state, with forecasters warning the Monterey Peninsula could be cut off and the whole city of Salinas — home to 160,000 people — flooded.

"The entire lower Salinas Valley will have disastrous flooding," the National Weather Service said.

"The entire city of Salinas is in danger of flooding. Most of Castroville will flood. All roads near the Salinas River will be flooded and impassable. 90,000 acres or more of agricultural land in the Salinas Valley will have disastrous flooding.

"Many roads, homes and agricultural land areas in the Salinas Valley will have major flood damage."

At least 19 people are known to have died as communities have struggled to cope with the constant deluge.

READ MORE: Cyclone gyrating off California threatens new floods in 'soaked' region

Salinas River's rage

The Salinas River, already swollen by weeks of torrential rain, was expected to peak sometime on Friday, breaching its banks in a flood that could last until Sunday.

Evacuation orders and warnings were widespread, with forecasters saying major roads could become impassable — including highways that link the Monterey Peninsula with the rest of the county.

"Residents both on the peninsula and in the Salinas area should expect to be cut off for two to three days," Monterey County officials said earlier this week.

Monterey County Sheriff Tina Nieto told reporters on Thursday that residents were being warned they could be trapped by the floodwater.

Hundreds of thousands of homes and businesses have been left without power at various times as infrastructure has taken a battering.

And it's not over yet, forecasters say.

READ MORE: Landslides, sinkholes, floodwaters plague California as more storms loom

Twenty-third year of drought

"The ongoing unsettled weather in the West associated with the active Atmospheric River pattern, unfortunately, continues into this weekend with another couple rounds of heavy precipitation forecast," the NWS said.

Over the mountains, that was translating into snow, with more than a metre expected over the weekend in the Sierra Nevada range, making travel dangerous or impossible.

Among the 19 to have died were drivers who have been found in submerged cars, people struck by falling trees, a husband and wife killed in a rockfall, and people whose bodies were discovered in floodwaters.

Winter storms are not unusual in California, where most of the annual rain comes in a fairly concentrated period.

But global heating, driven by the industrial-scale use of fossil fuels, is supercharging storms, making them wetter and wilder.

At the same time, the western United States is aridifying, with much of the region in the 23rd year of a drought.

Hydrologists say the recent rains are helping — California has received an average of almost 23 centimetres of rain since late December — but are not a fix.

READ MORE: California faces more storms and potential floods