Southern California braced for the impacts of Tropical Storm Hilary, as it brought strong gusty winds and heavy rain on Aug. 20.

California Governor Gavin Newsom declared a state of emergency for much of Southern California, with flash flood warnings in place until the early hours of Aug. 21.

Hilary is the latest climate-related disaster to wreak havoc across the U.S., Canada and Mexico. Hawaii's island of Maui is still reeling from a blaze that killed more than 100 people, making it the deadliest U.S. wildfire in more than a century. Firefighters in Canada are battling that nation's worst fire season on record.

Hilary first made its landfall in Mexico's Baja California, as a powerful Category 4 hurricane, before weakening to a tropical storm before crossing into California. No fatalities or significant injuries were reported in the U.S. One man was killed in Mexico when his family was swept away while crossing a stream, Mexican officials said.

Scientists still don't know why some storms, like Hilary, get big and some stay small, said MIT hurricane scientist Kerry Emanuel.

"It's quite unusual for an Eastern Pacific storm to be so large since they are usually small and stay deep in the tropics," said University of Albany atmospheric scientist Kristen Corbosiero, an expert on Pacific hurricanes.

Hilary arrived in California as a rare tropical storm that dumped 4 to 5 inches (10 to 12 cm) of rain on coastal areas and 10 inches (25 cm) or more in the mountains, National Weather Service meteorologist Richard Thompson said. He called it the first landfallen tropical storm in Southern California since Sept. 25, 1939.

The storm moved on a more easterly path, and this brought higher amounts of rainfall to the desert as opposed to coastal areas. The higher elevation areas such as Palomar Mountain and Mt. Laguna also received significant amounts of rain, as much as 7 inches-plus.

As reported by the Steele-Burnand Anza-Borrego Desert Research Center, the 2.07 inches of rainfall recorded at Anza-Borrego Desert State Park headquarters made August 20, 2023, the second wettest day of the past 11 years (going back to the installation of the automated, on-line weather station). It is surpassed only by The Valentine's Day Massacre of February 14, 2019 (2.71 inches).

The thunderstorm also brought a couple of power surges, with luckily, no downed poles affecting SDG&E services.

The S-22, Borrego Salton Sea Way was closed for a few days due to flooding. Also, Yaqui Pass was also closed briefly due to flooding at Highway 78 by Tamarisk Grove. Interstate 8 also had some signifiant rock slides in the In-ko-pah gorge area, with massive boulders that closed lanes until they could be removed.

Clark Dry Lake still has about 3 – 5 inches of water as a result of Hilary and that means Fairy shrimp appearing. It's somewhat rare.

Hilary shattered daily rain records in San Diego and likely dumped the equivalent of a full year's worth on Death Valley National Park, forcing the park to be closed indefinitely and leaving about 400 people sheltering at Furnace Creek, Stovepipe Wells and Panamint Springs until roads could be made passable, park officials said.

The Coachella Valley - which was under an unprecedented tropical storm warning until it was lifted around 2 a.m. on Aug. 21 - experienced heavy flooding and other damage after Tropical Storm Hilary churned through the region. It left several roads closed and a ton of significant clean-up work. The results of the storm also left many phone lines down in the cities of Palm Springs, Cathedral City, and Indio.

Over 7,000 Imperial Irrigation District customers were without power, with storm-related power outages reported across the district's eastern Coachella Valley and Imperial County service area. Between about 5:30 and 7 p.m., IID reported roughly a dozen separate power outages on its social media accounts, including 1,693 customers in El Centro, 1,107 in the Westmorland/Calipatria area, and 1,190 customers in two different areas of Indio. This caused many school districts in the area to postpone the opening of school for the first day.

Remnants of Hilary were expected to dump heavy rains in Nevada and Utah and into the Northwest, where more than 4 million people remained under the threat of flooding until Monday night, the service said.

"Fortunately, Californians listened to their local officials and took the necessary preparedness actions to help protect themselves and their families," FEMA administrator Deanne Criswell told reporters aboard Air Force One.