Some "brutal" weather was bearing down on California on Tuesday, with forecasters warning torrential rain and widespread flooding this week could prove deadly.

The usually parched west of the United States has been walloped by a series of storms over recent weeks that have lashed the coast, bringing near-record rainfall to some parts.

Now a huge system is set to roll in from the Pacific Ocean over Wednesday and Thursday, with meteorologists saying anyone living in its path needs to be prepared.

"This will likely be one of the most impactful systems on a widespread scale that this meteorologist has seen in a long while," one National Weather Service (NWS) forecaster wrote.

"The impacts will include widespread flooding, roads washing out, hillside collapsing, trees down (potentially full groves), widespread power outages, immediate disruption to commerce and the worst of all, likely loss of human life.

"This is truly a brutal system that we are looking at and needs to be taken seriously."

Parts of northern California are already reeling from a powerful storm that hit on New Year's Eve, causing landslides and power outages, as levees were breached and roadways were flooded.

At least one person is known to have died after being trapped in a submerged car.

San Francisco recorded almost 5.5 inches (14 centimeters) of rain on December 31, the second wettest day for the city in recorded history.

Light rain was falling in the region Tuesday, expected to turn heavy on Wednesday, with up to five inches forecast around Sacramento, the NWS said.

"A strong storm system & atmospheric river will bring widespread moderate to heavy rainfall & strong winds to the region from Wed-Thurs. This will increase the threat for widespread flooding and wind damage across the Bay Area & Central Coast," NWS Bay Area tweeted.

The agency said people living in areas affected by the storm should have a "go bag" ready so they can evacuate quickly, and warned of the dangers of mud or rockslides near hills.

The rain is the result of an atmospheric river — a current of heavy moisture in the air.

Such atmospheric rivers are not uncommon at this time of year, but the present one is connected to a low pressure system that will develop into a "bomb cyclone" — where air pressure drops suddenly, generating intense winds.

Heavy rain in lower lying areas will turn into heavy snowfall over the mountains as moisture-laden air rises, with up to four feet (1.2 meters) expected over the Sierra Nevada.

The western United States is in the grip of a decades-long drought, with below average precipitation leaving river and reservoir levels worryingly low.

While forecasters say any rain is helpful, sudden downpours brought by heavy storms can do more harm than good as the ground struggles to absorb such high volumes of water so quickly, resulting in flooding.

Marvel actor Renner says 'messed up' after snow plow accident
Los Angeles (AFP) Jan 4, 2023 –

Marvel superhero actor Jeremy Renner said Tuesday he was "messed up" after being run over by his own snow plow as he tried to climb into the driver's seat of the giant 14,000-lb (six-ton) vehicle.

Renner suffered severe injuries Sunday morning near his Nevada home while attempting to halt the PistenBully machine, which had begun rolling forward after he used it to help free a stranded family member's vehicle from heavy snow.

"In an effort to stop the rolling PistenBully, Mr Renner attempts to get back into the driver's seat," Washoe County Sheriff Darin Balaam told a press conference.

"Based on our investigation, it's at this point that Mr Renner is run over by that PistenBully."

Renner, who was taken by helicopter to nearby Reno, posted a selfie Tuesday from his hospital bed, showing heavy bruising on his face.

"Thank you all for your kind words. I'm too messed up now to type. But I send love to you all," wrote Renner on Instagram.

Renner's publicist Sam Mast said the actor had undergone surgery and was "making positive progress and is awake, talking and in good spirits."

"He remains in ICU in critical but stable condition," Mast said.

"He is overwhelmed by the showing of love and support. The family asks for your continued thoughts while he heals with his close loved ones."

Officials at Tuesday's press conference said there was no indication that drink or drugs were involved in the incident, which was being treated as a "tragic accident."

Sheriff Balaam said an investigation was ongoing due to the "severe injuries" Renner suffered, including checks for any sign of mechanical failure.

The PistenBully, or snowcat, operated by Renner is a large specialized snow plowing vehicle with giant, raised caterpillar tracks on each side of an enclosed cab.

Balaam said emergency responders struggled to reach Renner due to three feet (one meter) of snowfall the previous night, which forced several drivers to abandon their cars on a nearby highway.

On arriving, they treated Renner, and "some good neighbors of Mr Renner's… came out with some towels and rendered some aid."

The sheriff praised Renner as a "great neighbor" who had been using his machine to plow private roads for nearby residents.

Renner holds the honorary title of deputy sheriff and is popular with local children, who call him "Hawkeye" after the superhero he plays in several Marvel films and a recent miniseries, Balaam added.

Renner, 51, has been nominated for two Oscars for his roles in "The Hurt Locker" and "The Town."