A stunning storm: Historic downpours, evacuations reported in Southern California

A slow-moving Pacific storm prompted evacuations Thursday in cities and beach towns along California's southern coast as streets were submerged beneath floodwaters.

The cities of Oxnard and Port Hueneme — both in Ventura County, west of Los Angeles — issued evacuation orders for some coastal areas and at least one shelter was opened for residents fleeing their homes. The Oxnard Fire Department has executed water rescues and, along with the police department, has asked residents to stay off the roads due to widespread flooding. There have not been reports of any injuries or deaths. A brief tornado warning was issued for Ventura County overnight.

The brunt of the storm damage appeared to be in the beachside city of Port Hueneme, according to the Ventura County Star, part of the USA TODAY Network. Roughly 60 homes in a senior community there were evacuated overnight.

Crews there were working to clear drains and keep the water moving as the rain continued to fall throughout the morning, said Port Hueneme City Manager James Vega. A damage assessment also was ongoing. “We had just a massive amount of rain very quickly, and it overwhelmed our drainage system,” Vega said.

A 'dramatic' storm

“This is a genuinely dramatic storm,” climate scientist Daniel Swain, of the University of California, Los Angeles, said in an online briefing. “In Oxnard, particularly, overnight there were downpours that preliminary data suggests were probably the heaviest downpours ever observed in that part of Southern California.”

National Weather Service meteorologist Mike Wofford told the LA Times that “the frequency of this kind of event is on the order of once in every thousand years."

In an advisory, weather service meteorologists said at least 2-6 inches of rain had fallen over the Ventura County area. An additional 1-4 inches was expected to fall by the afternoon. Meteorologists anticipate rock and mudslide activity on and below canyon and mountain roads, leading to “significant travel delays.”

“It was a very, very significant amount of rainfall being produced in a short amount of time,” Ariel Cohen, a meteorologist in charge at the weather service's office in Oxnard, told the Ventura County Star. Rainfall rates – which can cause flooding at 1 inch per hour – reached as high as 3 inches per hour early Thursday, he said.

The storm was not over: In all, some 27 million people live where a flood watch remained in effect Thursday afternoon, including much of the Los Angeles and San Diego metro areas.

Developments:

◾ At Los Angeles International Airport, 40 flights have been delayed and one canceled as of 1:30 p.m., according to FlightAware.us.

◾ The Oxnard Union High School District, which has schools across Ventura County, remained open despite the storm conditions Thursday morning. Oxnard and Hueneme elementary and middle schools are on winter break, according to the districts' websites.

◾ About 20 residents of a senior community in Port Hueneme were evacuated early Thursday, county Firefighter Andy VanSciver told the Ventura County Star. About 10 were rescued in a tactical rescue vehicle.

◾ Oxnard Fire Department reported cars stuck in flooded roadways and several water rescues. There have not been any reports of injuries or deaths in Ventura County. "Many of the streets and intersections are heavily impacted by flooding," read a post on X by the fire department. "Please stay off the city streets for the next several hours until the water recedes. Standing water can cause vehicles to stall and may become trapped."

Santa Barbara under flash flood warning

The National Weather Service issued a flash food warning for south Santa Barbara County that'll remain in effect until 4 p.m. local time. Meteorologists urged the estimated 233,800 people in the area to move to higher ground and avoid driving through flood waters.

"This means that flash flooding is occurring or imminent," read a statement from the Santa Barbara Police Department. "A flash flood is an extremely dangerous, sudden, violent, and fast-moving wall of water. ... If you are in one of these areas, go to the innermost room of your home or to higher ground such as a second floor."

Weather in Los Angeles to pick up through the evening

Los Angeles will be hit the hardest by rain and strong winds beginning Thursday afternoon and continuing into the evening, according to AccuWeather. Through the night and into Friday, the area between San Diego and Palm Springs will be drenched, raising concerns over potential flooding.

Coastal areas in Los Angeles and San Diego are expected to receive 2-5 inches of rain, while mountainous areas will get around 5-10 inches, according to the NWS. Wind gusts around 25-40 mph are expected, but some could reach up to 55 mph.

As of Thursday morning, 1.5 inches of rain was recorded at Los Angeles International Airport, according to AccuWeather. Of that amount, 0.72 of an inch of rain fell on downtown Los Angeles.

This is the the area's first El-Niño influenced storm, one that's fueled by an atmospheric river of moisture, the National Weather Service said. It's expected to be the biggest rainstorm for the region since Hurricane Hilary dumped up to half a foot of rain in August, AccuWeather forecasters said.

Storm first caused flooding throughout Northern California, tornado in Oroville

The same storm has been drenching areas in Northern and Central California into midweek while remaining largely offshore over the Pacific. Parts of Sacramento flooded, with entire roadways under water, as the storm moved southeast Tuesday and Wednesday.

Oroville, a city about 65 miles north of Sacramento, experienced a tornado on Tuesday with winds of up to 90 mph and which lasted two minutes, according to the NWS. While no one was hurt or injured, the tornado damaged at least one building and downed trees.

Contributing: Doyle Rice, USA TODAY; Associated Press

This article originally appeared on USA TODAY: Pacific storm in Southern California brings rain, floods: Updates