California under life-threatening flood threat after heavy rain, winds

Southern California experienced heavy rain and flash flooding due to a powerful atmospheric river, prompting Governor Gavin Newsom to declare a state of emergency in eight counties, including Los Angeles and Orange County.

LA and San Bernardino County also declared their own states of emergency, CNN reported.

"Los Angeles County is taking action to protect our communities during the storm and to recover from any impacts that may result," said Los Angeles County Board of Supervisors Chair Lindsey P Horvath.

Following Sunday’s flooding, over 11 million people in California are at high risk of life-threatening flooding with parts of the Los Angeles area forecast to receive close to half a year’s worth of rain by Tuesday.

Over 900,000 California power customers experienced outages due to heavy rain and strong winds from an intense atmospheric river, as officials warned of one of the "most dramatic weather days in recent memory."

Atmospheric rivers are wide-reaching plumes of moisture that act like firehoses, tapping into warm, moist air from the tropics, and releasing heavy rainfall and snow over land.

These storms are common on the West Coast during winter, but weaker rivers provide essential rainfall and snow during the wettest months of the year.

This rainfall and snow are crucial for western water supplies, filling reservoirs during hot summers.

However, excessive rainfall from storms can increase flooding risks, especially when a series of storms occur in sequence with little time for drying out between.

Last week’s atmospheric river broke multiple rainfall records across California and triggered road closures and water rescues.

Atmospheric rivers can also impact the eastern US and happen frequently in parts of Europe, Africa, Australia and New Zealand.