A huge storm system dumped record amounts of rain on southern California and prompted concern the poor weather could spread across the US.
The deluge came at the end of a week that saw Los Angeles receive half its annual rainfall in just six days.
Hundreds of people were evacuated in the city's suburbs, with particular concerns for homes in steep-sided canyons previously ravaged by wildfires. Flood warnings and emergency orders have also been put in place in Arizona, Nevada and Utah.
There are concerns that the weather system will spread across the US, reaching New Mexico by Thursday and the Gulf Coast by the end of the week. California Governor Arnold Schwarzenegger declared a state of emergency in half a dozen communities after heavy rain and snow.
He said the storms were "likely to be beyond the control of the services, personnel, equipment and facilities of any single county, or city."
An estimated 17 feet of snow has fallen in less than a week at one monitor station in California's Sierra Nevada mountains, according to the US meteorologists. "The ground is so saturated it could move at any time," said Bob Spencer, spokesman for the LA County Department of Public Works.
The heavy falls in California have brought relief from the state's drought, with water storage in California's seven reservoirs rising by two-thirds on last year's levels following the downfall.