At least 14 people have died in California as a fierce storm brings torrential downpours, high winds and flooding to the state.

Thousands of people have evacuated their homes, while millions more are under severe weather warnings.

Nearly 188,000 homes and businesses were without electricity, according to data from Poweroutage.us.

Heavy rain is forecast to last much of the state throughout Tuesday, with some areas at risk of dangerous mudslides.

The National Weather Service (NWS) has described it as "the most impressive storm since January 2005".

The weather is expected to dump up to 7in (18cm) of rain in some parts by Wednesday and could produce additional flooding, mudslides and landslides. particularly in areas previously hardest hit by heavy rainfall, NWS officials warned.

"An enormous cyclone" is developing off the coast, officials said.

A five-year-old, who was swept away by floodwaters near Paso Robles on Monday, is still missing.

The boy and his mother were reportedly in a truck taking him to school when the vehicle was overcome by water. It sparked a seven-hour search that was called off when the conditions became too dangerous for divers. He has not been declared dead, local officials said, however details of when the search will resume have not been given.

Around 90% of Californians - some 34 million people in the most-populous US state - are under flood watch, according to the National Oceanic and Atmospheric Administration.

"This is not a day to be out doing anything you don't have to," Santa Barbara County Sheriff Bill Brown told the Los Angeles Times.

An order issued on Monday afternoon by the Montecito Fire Department directed residents of the town and nearby canyons: "Leave now!"

Residents unable to flee were told to move to their innermost room or high ground. (BBC)