• Motorists stranded in cars after rivers burst their banks
  • Mudslides feared in mountainous areas
  • State prepares for seventh straight day of torrential rain
  • Cause is freak 'atmospheric river' that occurs once over few hundred years
  • One-third of state's annual average rainfall pours down in a week
California is bracing for another monster storm tonight after days of relentless rainfall forced officials to evacuate hundreds of homes in America's so-called Golden State.

Governor Arnold Schwarzenegger announced a state of emergency for the worst hit areas today and rescue crews frantically tried to clear flooded roads before more thunderstorms, hail and even small tornadoes hit the region.

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© ReutersSwept away: A member of the Los Angeles Fire Department drives a watercraft in the LA River after two victims were reported to be swept away in the water today. The search eventually had to be called off due to the weather
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© Getty ImagesDesperate measures: Jennifer Bowerman and her son Sabastian, seven, are led across flood waters on a raft after being stranded in a hotel in San Diego today during the rainstorm
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© Associated PressNo go: Locals secure a van to prevent it from being swept into a river in Silverado Canyon in California today

In a part of the world that takes shirtsleeves winter weather for granted, the week-long bout of heavy rain has caused Christmas chaos.

Officials ordered evacuation of 232 homes in the foothill suburbs of Los Angeles amid fears of mudslides, power was down in many communities and the downtown area of picturesque Laguna Beach was cut off by floodwater that stripped away sand from the shoreline.

Tonight residents are bracing themselves for even worse.

Forecasters are warning that rain could be falling at the rate of two inches per hour while 55 mph winds could turn into tornadoes as the weather front, called an 'atmospheric river' by scientists, continues to pound the coastal state.

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© Agence France Presse/Getty ImagesDangerous driving: Cars make their way through the flooded streets of Los Angeles today
A similar weather pattern is said to have brought 45 straight days of rain to the state in 1861. It caused flooding of Biblical proportions, recalling the tale of Noah and the ark, and the damage it caused bankrupted the state.

'It's going to be a three-ring circus," said National Weather Service spokesman Bill Hoffer. 'There's going to be a six-hour time frame when it's really going to be dumping on us.'

'Especially through the morning commute, it's likely to be very wet and the roads will be a mess,' said Jamie Meier, spokeswoman for the National Weather Service.

'People should really stay in tune with their local weather sources and be apprised of changing conditions.'

california flood
© Getty ImagesSubmerged: A car sits partially underwater after the San Diego River burst its banks
california flood
© Associated PressDisruptions: People attempt to pull a truck out of the rain-swollen Santiago Creek near Modjeska Canyon in California yesterday
'We'll keep our fingers crossed, but the more rain that comes, the possibility of mudslides is definitely real,' said Jim Amormino, spokesman for the Orange County sheriff's office, which has rescued nine people from the flooding in the past 24 hours.

'We've been lucky so far, but I'm not sure how much longer the luck will hold out.'

While the threat of tornadoes may sound more dangerous, the real concern is mudslides.

Much of the northern Californian hillsides that were stripped bare by wildfires earlier this year have lost the vegetation which holds soil in place.

The downpours are expected to move that loose soil and send it flooding downhill towards residential areas.

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© Associated PressNice brisk morning walk: Priscilla Newton reaches down to recover her boot from the mud on Pacific Coast Highway in Laguna Beach, California today. Water filled the streets of Laguna Beach today
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© Associated PressNature as art: An 'Urban Light' sculpture showing a collection of street lights from many eras is reflected in the Los Angeles rain
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© unknownThe real danger: A rock slide is seen along the Pacific Coast Highway at the Ventura County line yesterday
'Mudslides are a significant risk for three years after a fire and are especially likely anytime the rainfall rate reaches or exceeds one inch per hour,' said Susan Cannon, of the U.S. Geological Survey.

With rain falling up and down the state, Mammoth and other Sierra Nevada ski resorts boasted record December snowfalls of up to fifteen-and-a-half feet.

There have been two deaths since the storms began, a three-year-old boy and a 22-year-old man both killed in rain-related road accidents.

Rescuers had to pluck some stranded motorists from rain-swollen creeks. Shoppers dodged puddles while buying last-minute Christmas gifts. Disney resorts cancelled a plan to shower already soaked visitors with artificial snow.

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© unknownTravel danger: A rain-swollen Silverado Creek runs beneath Black Star Canyon Road in California yesterday
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© Associated PressThe Sodden State: A Porsche navigates a flooded drive in Oakland, California yesterday as heavy rains pour down on the state
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© Associated PressLet's take a dip: A pedestrian wades through flooded streets in Los Angeles yesterday... and there is more rain to come
In Orange County, four hikers missing overnight in a flooded canyon in the Cleveland National Forest were rescued by helicopter after their car was trapped along swollen Trabuco Creek.

Rescuers used a bulldozer to retrieve five other people who became stranded by the creek.

Downtown Los Angeles has already received more than a third of its annual average rainfall in less than a week.

Parts of the San Gabriel Mountains got more than eighteen inches of rain since Friday, with coastal cities like Santa Monica and Long Beach getting more than six inches, the US National Weather Service said.

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© unknownMap: This satellite image shows the rain and snow over California
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© National Weather ServiceClouded over: A radar image from the National Weather Service shows clouds covering nearly the entire state of California
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© Associated PressClean up: A worker begins to repair the damage after a tree fell on a house
Major rains in California can have deadly consequences.

In 2005, five days of near constant rain left at least 28 dead in mudslides and drownings.

One mudslide has already closed on street in the La Jolla area of San Diego while further inland, in Riverside, a surge of water swept through a homeless camp near the banks of the Santa Ana River.

Three people suffered minor injuries and about 50 lost all their belongings in the flood, according to Ruth Record of Come As You Are Homeless Ministries.

Rebecca Truver, 45, was in her tent when her dog and her cat started acting strangely and said, 'They knew something was happening.

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© Associated PressSoaked: Visitors leave Disneyland draped in rain gear
Disneyland Rain
© Associated PressWashout: Disneyland cancelled its daily parade and the fake snow storm that usually marks the festive season
'Then all of a sudden the water came through up to my knees.'

For all the perils of the torrential rains, there was a silver lining: The water is expected to help ease the effects of years of drought.

Tomorrow is expected to be dry, with sunshine and there will be light rain on Christmas Day in parts of California.
The Rain That Just Won't Stop: What is Happening in California?

The continuous rainfall pouring onto California is the result of what scientists call an 'atmospheric river'.

The term was only coined recently, within the last generation of satellite imaging, but there's nothing new about the phenomenon.

Scientists now believe it was an atmospheric river that brought 45 straight days of rain to the state in 1861-62.

It caused flooding of Biblical proportions, recalling the tale of Noah and the ark, and the damage it caused bankrupted the state.

The plans to combat this type of severe storm have been christened 'Ark Storm'.

'The atmospheric river brings in the moisture. How much rain gets dropped out of it has a distribution, just like earthquakes,' said Lucy Jones of the U.S. Geological Survey office in Pasadena.

In the U.S. Jones is usually recognised as an earthquake expert but her team at the USGS Multi-Hazards Demonstration Project develops computer models for a variety of natural disasters.

They have just finished a scenario for a modern day 'Ark Storm' scenario akin to the 1861-62 storm.

'We actually made a model of this type of storm, just like we made a model of a Southern San Andreas Earthquake,' said Jones explained.

'We used the same techniques to try to assess what the damage would be.

'And our conclusion is that the storm would cost about four times as much as the shakeout earthquake.'

Fortunately, such extreme storms are relatively rare, though lesser atmospheric rivers have also caused severe damage storms, notably in 1969 and 1986.

Jones said more moderate atmospheric rivers occur on an annual basis and that one of the size currently battering California happens perhaps once a decade.

Another U.S. natural disaster expert, Bill Patzert, is struck by the coincidence that California's last major Ark Storm occurred so close in time to the last Southern San Andreas earthquake - known as 'the Big One' - in 1857.

It seems both extreme natural events occur every few hundred years.