Humboldt County Sheriff official in flooded waters in Freshwater, Calif. on Sunday.Humboldt County Sheriff`s Office

At least one person has died in Redding, California, due to the torrential rain and significant flooding as the state braces for worsening conditions this week.

Redding Mayor Mike Littau confirmed the fatality in a Facebook update posted Sunday night, noting that local police and fire officials were conducting water rescues. Details about those recues are not immediately clear.

"Fire Chief and staff will be setting up an Emergency Operations Center to help coordinate flooding response," Littau added in the statement. "Public Works and REU are all out on streets trying to get them cleared and power back on."

A striking video taken in Redding on Sunday shows roadways submerged by flash flooding and what appears to be a water main break, causing a massive plume of water to erupt from the ground.

As of Monday morning, flood watches remain in effect for 41 million people across California, stretching from the northern part of the state to the Mexican border.

Cities at risk include San Francisco, Los Angeles and San Diego.

A potent atmospheric river is fueling the flooding and will continue throughout the week, with the moisture plume beginning to move toward Southern California.

San Francisco`s watch will run from Monday morning through late Thursday, Los Angeles from Tuesday afternoon to late Wednesday and San Diego from early Wednesday through Thursday.

Flash floods on Old Oregon Trail in Redding, Calif. on Sunday.Ronda Snyder

On Monday, bands of moisture will target north-central California into the northern Sierra, which can expect to see 2 to 4 inches of rainfall. Higher elevations will be hit with heavy mountain snow and strong winds, creating dangerous travel conditions.

Torrential rain will pass over the northern California coastline on Tuesday before moving into parts of southern California.

By Christmas Eve, treacherous travel conditions are possible across California, with the heaviest rain in the southern part of the state from Santa Barbara to Oceanside.