Southern California and U.S. Southwest at Risk for Flash Flooding and Landslides After Storm Hilary

LOS ANGELES, (Reuters) – Parts of Southern California and the U.S. Southwest on Monday faced the threat of flash flooding along with landslides and mudslides after storm Hilary unleashed record-breaking downpours overnight.

Some 17 million Americans were under flood and high-wind advisories, watches and warnings as remnants of the storm moved north, dumping heavy rains from the California-Mexico border up through Las Vegas and into parts of the Northwest, the National Weather Service said.

One of the hardest hit communities has been Palm Springs, California, where video footage posted on social media showed flooded streets and debris flows. Mayor Grace Garner told CNN the city’s 911 emergency system was knocked out by the storm.

“Right now we have flooding on all of our roads. There’s no way in or out of Palm Springs, and that’s the case for the majority of the Coachella Valley. We’re all stuck,” she said during an interview on the network.

A steady rain fell on Monday morning in many parts of the region, where record-breaking downpours had already fallen. Hilary was downgraded to a post-tropical cyclone overnight.

Some mountain and desert areas could see rain accumulation totals reaching 5 to 10 inches (12 to 25 cm) from the storm, as much as the deserts typically see in a year, forecasters said.

The rain was expected to slowly dissipate throughout the morning in Southern California, but officials warned residents not to let their guard down as dangerous flooding could wash out roadways and inundate neighborhoods.

“The ongoing and historic amount of rainfall is expected to cause life-threatening to locally catastrophic flash, urban and arroyo flooding including landslides, mudslides and debris flows today,” the weather service said.

Some 400 flights in and out of airports across the Southwest were canceled or delayed on Monday morning, including 100 landing at and taking off from San Diego International Airport, according to Flightaware.com.

California Governor Gavin Newsom declared a state of emergency for much of Southern California while President Joe Biden ordered federal agencies to move personnel and supplies into the region.

Before striking the U.S. Southwest, the storm passed northward through Mexico’s Baja California peninsula. It killed at least one person in Mexico, triggered flash flooding and swept away roads.

It crossed the border on Sunday afternoon, hitting San Diego County with its first tropical storm ever recorded and becoming the first to pelt Los Angeles County since 1939.