At least three people have been killed by falling trees as a powerful storm drenches California bringing flooding, mudslides and power outages. Fire officials have responded to over 130 flooding incidents and conducted several rescues since the deluge began. Forecasters say heavy rain with life-threatening flash flooding will continue into Tuesday. The record-breaking rainfall has led the governor to declare a state of emergency in eight counties. The storm is due to an "atmospheric river" effect, a phenomenon in which water evaporates into the air and is carried along by the wind, forming long currents that flow in the sky like rivers flow on land. This slow-moving storm is the second atmospheric river to hit California in two weeks. Officials have issued evacuation orders for some hilly neighborhoods in the south of the state, including in Los Angeles, where city leaders declared an emergency. "It is vital now more than ever, stay safe and off the roads," LA Mayor Karen Bass said on Monday. "Only leave your house if it is absolutely necessary." Farther north, San Francisco, one of the hilliest cities in the world, and its surrounding areas have seen landslides. Three men have died from tree falls, including one in Sacramento Valley, and another when a tree toppled on to a home in Santa Cruz County, officials said. An elderly man died in Yuba City in Northern California when a redwood tree fell in his backyard. The same storm system also dumped very heavy snow across the region. On Monday, an avalanche hit a ski resort in Lee Canyon near Las Vegas, Nevada, though no-one was hurt. Mudslides and debris flows have been reported in the Los Angeles area. On Sunday, 16 residents were forced from their Hollywood Hills homes after mudslides flowed through houses, knocking buildings off their foundations and rupturing gas lines. Witnesses have reported seeing refrigerators and pianos flowing through streets amid the debris. Damage was also reported in the upmarket Bel Air and Beverly Hills neighbourhoods of LA. Drivers stranded by flooding in Los Angeles and San Bernardino County had to be helped by rescuers. A father, mother and daughter were forced out of their car early on Monday and were able to climb into a tree to escape the rising flood waters, according to San Bernardino fire crews. Rescue services on the coast came to the aid of 19 boaters who became stranded on rocks near the Long Beach breakwater after their 50ft (15 meters) sailboat lost its mast in gale-force winds. Lifeguards sent rescue swimmers to make contact with the group, who were then assisted into rescue boats with only one person suffering non-life threatening injuries. Strong winds of up to 70mph (112km/h) have also caused power cuts and downed trees, though gusts were forecast to decrease significantly by Monday night. It follows what has already been a record-setting day for the state. The National Weather Service (NWS) said that on Sunday, 4.1in (10.4cm) of rain fell in downtown Los Angeles, surpassing the previous record of 2.5in set in 1927. By Monday afternoon, parts of LA County had recorded over 11in of rain since the weekend — approaching the nearly 15in that the region normally experiences in an entire year. The storm underwent bombogenesis, meaning that colder air mixed with warmer sea air, leading to a swift drop in atmospheric pressure, creating a so-called "bomb cyclone," according to UCLA climate scientist Daniel Swain. Over 100mph winds were recorded in the Bay Area, he said in a briefing on Monday. The storm and associated flooding has also forced schools to close from Malibu to Sonoma County, near San Francisco. — BBC
