Hilary makes landfall in Mexico's Baja California peninsula as rain begins in Southern California (2023)

Tropical Storm Hilary made landfall Sunday in the northern part of Mexico's Baja California peninsula as officials warned "catastrophic and life-threating flooding" in that region and the southwestern U.S.

Hilary was downgraded a few hours earlier to a tropical storm as rain from the storm startedspreading in Southern California, the National Weather Service said.

As of 12 p.m. ET / 8 a.m. PT, the storm had maximum sustained winds of 70 mph. It is the first time ever that the National Hurricane Center to issue atropical storm warningfor Southern California, and California Gov. Gavin Newsom declared a state of emergency ahead of the storm.

Los Angeles county officials held a press conference early Sunday where they said they were expecting 1 to 3 inches of rain and wind speeds of 20 to 30 mph.

"We are ready," Los Angeles Mayor Karen Bass told "Face the Nation."

Tropical storm conditions are expected to begin later Sunday in the southwestern U.S., with gusty winds expected to spread well inland. The National Hurricane Center said large swells are expected to effect portions of the Baja California peninsula as well as southern California over the next several days. The California Department of Parks and Recreation on Saturday ordered a temporary closure of all San Diego and Orange County state beaches and several state parks.

• Latest storm coverage from CBS Los Angeles

Disneyland announced Saturday that the parks would be closing early on Sunday, with Disney California Adventure Park closing at 9 p.m., Disneyland Park closing at 10 p.m. and the Downtown Disney District will close at 11 p.m.

Other parts of the southwestern U.S. were preparing, with the National Weather Service in Las Vegas warning on Sunday that strong winds were likely, as well as flash flooding.

By the time Hilary reaches California, it is forecast to have downgraded to a tropical storm, which is defined as having winds of at least 39 mph,according tothe National Weather Service.

However, it will stick pack a punch. Widespread "moderate to heavy" rain is expected into early Monday for Southern California, with a high risk of flash flooding that could include "landslides, mudslides and debris flow" in mountains and deserts, according to the National Weather Service in San Diego.

The weather service forecastedthat some areas had at least a 70% chance of experiencing flash flooding.

The tropical storm warning, which was upgraded Friday night from what was also the first-ever tropical storm watch for the region, is in effect for most of Southern California, including large swaths of San Diego, Orange and Los Angeles counties, along with California's Catalina Island, according to the National Weather Service.

L.A. County officials were advising all Catalina residents and visitors to leave the island as soon as possible Saturday ahead of the storm's arrival.

In its advisory, the NHC said that heavy rains were spreading north from Baja California to the Southwestern U.S. Saturday night. The agency warned that "catastrophic and life-threatening flooding" was "likely" for both regions.

Hilary is forecast to move close to the west-central coast of Mexico's Baja California Peninsula Saturday night into Sunday morning, and then move across Southern California Sunday afternoon into Sunday night, the NHC said.

"As of now right, what we know for certain, is that there will be sustained high winds of 50 mph, and that there will be enough rain to flood low-lying areas," San Diego Mayor Todd Gloria said in a news briefing Saturday afternoon.

Gloria said that forecasters were predicting that "the most intense portion" of the rain would hit San Diego Sunday afternoon, and he implored the public "to avoid areas that are known to be flood zones."

A White House spokesperson said that President Biden had been briefed on Hilary and that his team was working "with state and local agencies ahead of the storm." The president and his family are vacationing in Lake Tahoe in Northern California. The president and first lady Jill Biden are slated to travel to Hawaii Monday to survey the destruction from the Maui wildfires.

• How to prepare for hurricane season, according to weather experts

Forecasters said the storm is expected to produce 3 to 6 inches of rainfall, with maximum amounts of 10 inches, across portions of Mexico's Baja California Peninsula. The same rainfall amounts are expected across portions of Southern California and southern Nevada.

"It is rare — indeednearly unprecedentedin the modern record — to have a tropical system like this move through Southern California," said Greg Postel, a hurricane and storm specialist at the Weather Channel who has a doctorate in atmospheric sciences.

Postel said there will likely be "damaging wind gusts," especially at higher elevations, in the area, and swells along the coast.

California was drenched by a historic amount of rain this winter after being hit with an unprecedented number of atmospheric rivers. Chris Heiser, emergency services director for the city of San Diego, told CBS News Friday that those storms may have helped prepare officials for what is to come from Hilary.

"That really allowed us to get a feel for what the impact of heavy rains and winds are," Heiser said. "But this one's got some unique features. The amount of rainfall is substantial, especially up in the mountains. And the majority of the population of San Diego is at the base of those mountains."

"We're looking at this to be a significant storm, possibly one of those that sets records, and so we're preparing accordingly," he added.

The Navy moved vessels out of San Diego Bay Saturday to avoid damage from the storm. Ships and submarines left Naval Base San Diego, Naval Base Coronado and Naval Base Point Loma and will remain at sea until Hilary passes over the region, the Navy said in anews release.

"In order to ensure the safety of our Sailors and ships, we are taking all necessary measures to mitigate potential damage to infrastructure and Third Fleet vessels caused by the storm," said Vice Adm. Michael Boyle, commander, U.S. Third Fleet, in the news release. "Safety remains our top priority, and putting all capable ships to sea makes it easier for us to manage the situation ashore."

California State Parks announced that all state beaches in San Diego and Orange counties would be closed Sunday and Monday, while the National Park Service closed the popular Joshua Tree National Park, located east of Palm Springs, through Monday evening over fears of flash flooding.

The city of San Diego followed suit with all city beaches and public buildings.

Los Angeles County Sheriff Robert Luna said in a news briefing that "swift water rescue personnel and rescue aircraft are on alert and ready for immediate response."

L.A. County officials also asked the homeless to stay away from waterways and river channels during the storm.

In San Bernardino County, located about 70 miles east of L.A., officials issued evacuation alerts for several mountain communities.

Nevada Gov. Joe Lombardo announced late Friday that 100 National Guard troops had been activated ahead of Hilary.

The San Diego Padres, Los Angeles Dodgers and Los Angeles Angels all had home games scheduled for Sunday. However, those games were shifted to Saturday double-headers in anticipation of the storm.

Capistrano Beach in the Orange County city of Dana Point Friday was one of several where crews built berms to protect the coastal community from high surf.

"We're getting ready now ahead of this event as it makes landfall to make sure we're prepared," said Chris Dargan, a spokesperson for California Governor's Office of Emergency Services.

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• Weather Forecast
• Mexico
• Hurricane Hilary
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