Another powerful storm has pummelled California, forcing thousands to evacuate and resulting in at least two deaths, while causing a levee to give way in coastal Monterey County.

"We were hoping to avoid and prevent this situation, but the worst case scenario has arrived with the Pajaro River overtopping and levee breaching at about midnight," Luis Alejo, a Monterey County supervisor, said on Twitter.

Residents told AFP they were alerted by local fire officials in the middle of the night that they needed to evacuate.

"Just the noise of the fire department -- their sirens and all -- woke us up," said Moses, a resident of the area for around 20 years who preferred to give only his first name.

He said officials later came and knocked on his door multiple times, but that he decided to wait until 5am to make a decision.

After returning home from surveying the flooding, Moses said water was beginning to cover his street.

"That's when I told my wife, 'hey, we got to get out of here'," he said.

The area remained under a flood warning yesterday afternoon, the National Weather Service said.

Many people were rescued from submerged cars

On Friday night, state emergency services director Nancy Ward announced that the storm had already claimed at least two lives.

Images posted on Twitter by the state's National Guard account showed guardsmen rescuing residents trapped in their cars by high water.

At least one road was washed away in Santa Cruz County, just north of Monterey.

Residents in several towns, mostly in the north, have been ordered to evacuate.

An unusually intense and seemingly endless series of storms has battered California for weeks.

The latest storm was expected to dump as much as 23cm of rain on already saturated ground.

President Biden has authorised federal aid for the area

Part of a powerful atmospheric river known as a "Pineapple express", for the warm, subtropical moisture it brings from Hawaii, this latest storm will speed the melting of the enormous snowpack that has built up in higher elevations.

The resulting runoff threatens to aggravate already serious flooding.

US President Joe Biden on Friday approved an emergency declaration that clears the way to expedite federal aid to the western state.

Mr Biden called Governor Gavin Newsom yesterday to reaffirm full federal support for the impact of flooding and landslides on the state, a White House pool report said.

Mr Newsom said California was "deploying every tool we have to protect communities from the relentless and deadly storms battering our state".