Hurricane Hilary makes landfall in the US

• Tropical Storm Hilary made landfall in the Southwestern US Sunday afternoon.
• The Category 4 hurricane has been downgraded to a tropical storm as of Sunday morning.

Tropical Storm Hilary made landfall in the US on Sunday afternoon, spreading heavy rains across California and Arizona, and could dump more than a year's worth of rain in parts of the southwestern US this weekend.

On Sunday afternoon, the National Hurricane Center said Hilary had maximum sustained winds of around 50 mph with higher gusts. The storm is expected to continue to weaken and become a post-tropical cyclone tonight.

The hurricane warning for portions of Mexico's Baja California peninsula has been discontinued but a tropical storm warning for areas of Southern California, mainland Mexico, Catalina Island, and northern Baja California is still in effect. The latter is a first-ever for the West Coast of the US.

"Heavy rainfall associated with Hilary could produce areas of flash flooding and result in landslides over portions of the Baja California Peninsula late tonight through late Sunday," the NHC said.

—NHC Eastern Pacific (@NHC_Pacific) August 21, 2023

Catastrophic and life-threatening flooding is likely, the NHC said.

Heavy rainfall is expected to peak Saturday night through Sunday night. The NHC warned of large swells off the coast and storm surges, as well as the possibility of tornadoes in southeast California, western Arizona, southern Nevada, and far southwest Utah.

As of 5:00 p.m. PDT, Hilary was located about 25 miles south-southwest of Palm Springs, California.

Powerful tropical-storm-force winds are also making their way over Southern California and Southwest Arizona.

Hilary remains a tropical storm, the NHC reported.

Evacuation warnings and orders have been issued for parts of Los Angeles County, Orange County, Riverside County, San Bernadino County, and Imperial County.

Potential for 'multiple years' worth' of rain

Rainfall, particularly in areas of Southern California and Southern Nevada, is expected to reach anywhere from 4-15 inches.

Areas in Nevada including regions near Las Vegas, Tonopath, and Reno will be affected.

"Across portions of Oregon and Idaho, rainfall totals of 1 to 3 inches with local maxima to 5 inches are expected through Tuesday morning, resulting in localized, some significant, flash flooding," according to the NHC.

Daniel Swain, a climate scientist at the University of California at Los Angeles, told CNN on Wednesday that "multiple years' worth of precipitation" could potentially fall in dry regions of California. Dry areas such as Death Valley, which usually receives around 2 inches of rain, could receive double that.

NHC also forecasts a high risk — at least 70% — for flash flooding near San Diego and Los Angeles on Sunday and Monday. Surrounding areas closer to Yuma and Las Vegas face moderate risks of at least 40%.

Hilary is the eighth named storm of the 2023 Pacific hurricane season and the third major storm to reach Category 4 this year. The last time a hurricane hit this area was 84 years ago, per CBS News.

An unusual Southwest cyclone as the climate crisis changes storms

This section of the country doesn't often see hurricanes and tropical storms for two reasons.

First, the wind patterns that create hurricanes usually push them out to sea instead of sending them toward the West Coast, Scientific American reported. Second, the water temperatures in the Pacific are usually cooler than those of the Atlantic, which means they don't have enough energy to churn up a storm.

The climate crisis is changing hurricanes, though. Scientists can't link any single storm to global warming without further analysis, but on the whole, rising global temperatures are driving a trend of increasing hurricane strength (aka windspeed), since cyclones feed on warm waters.

Storms can also bring more rainfall now, because a warmer atmosphere holds more moisture, as well as a higher storm surge due to sea-level rise.

Climate change may also be slowing down the progress of cyclones, meaning they sit over an area for longer, wreaking more destruction.

There are also signs of a northward shift in Pacific cyclones, according to the Center for Energy and Climate Solutions.

How to stay safe during a hurricane

As Hurricane Hilary makes its way toward land, those in its path should check out the NHC's hurricane preparedness website for how best to prepare. Even if the storm downgrades from a hurricane to a tropical storm with slower wind speeds, these extreme weather events still pose a threat to property and human life.

Some key tips the NHC advises include: Determine whether you live in an area prone to flooding. Also, check to see if you're in an evacuation zone. After that, take an assessment of your home. Being indoors is the first line of defense against extreme weather.

Does your home have any structural weaknesses that are especially vulnerable to strong winds? You may want to avoid those areas.

Since high winds can blow unsecured objects into your home, it may also be a good idea to clear things like propane tanks, bikes, or lawn furniture out of your yard. Protecting the integrity of your home may keep you safe from the worst of the storm.

These storms can also cause disruptions to your utilities, according to the CDC. You should do your best to have a supply kit that includes clean water, food, flashlights, batteries, government documents, and first aid materials.

Even with all these in order, you may receive orders to evacuate. To be prepared for this possibility, you should have a full tank of gas in your car, a prepped supply kit, and a radio or TV to get the latest updates on when and where it's safe to travel, per the CDC.