Drenching rains from post-Tropical Storm Hilary flooded parts of the southwestern United States on Monday as forecasters warned of life-threatening and catastrophic conditions from the rare storm as it moved inland.
The U.S. National Weather Service urged people to stay off roads in the Los Angeles area due to dangerous flooding. Mudslides were reported and roadways buckled from the flooding in some communities.
The National Hurricane Center said Hilary, designated a hurricane in recent days, has now diminished to a post-tropical cyclone. By late Monday morning, remnants of the storm were passing through southern California and the southwestern state of Nevada. Forecasters said the storm would then travel north through parts of Oregon and Idaho.
They warned that areas in the storm’s path could see 5 to 10 centimeters (1.96 to 3.93 inches) of rain and up to 30 centimeters (11.8 inches) in some isolated areas.
“Continued flash and urban flooding, locally catastrophic, is expected,” the Hurricane Center said. “Post-tropical Hilary is still expected to produce strong and gusty winds in and near areas of elevated terrain today.”
Many of the areas in the path of the weather system are not accustomed to seeing the type or rainfall associated with a tropical storm.
Tropical storms and hurricanes annually strike the southern and eastern shorelines of the U.S., but Hilary is the first tropical storm to hit the western U.S. coastline since 1997 and the first to hit Southern California since 1939.
Forecasters said some desert areas could end up with 12 to 25 centimeters (4.7 to 9.8 inches) of rain.
"In some places in the desert, that's a year's worth," senior meteorologist Alex Tardy told a news briefing. He works for the National Oceanic and Atmospheric Administration in San Diego. "The normal rainfall in Southern California and San Diego is nothing in August. So, a very unusual event is unfolding here."
Sunday was the wettest day on record in San Diego with 4.6 centimeters (1.81 inches) of rain.
In Palm Springs, California, the city's 911 emergency system was knocked out by the storm.
California Governor Gavin Newsom declared a state of emergency to help with response and recovery efforts.
President Joe Biden said his administration stood ready to provide assistance to California, Nevada and Arizona.
The storm forced the cancellation of flights in Los Angeles, San Diego, Phoenix and Las Vegas, while schools in Los Angeles and San Diego were closed Monday.
Tropical Storm Hilary made landfall Sunday on Mexico’s Baja California peninsula.
Meanwhile, forecasters are now watching Tropical Storm Franklin churning through the Caribbean Sea. Authorities in Haiti and the Dominican Republic warned residents to prepare for floods and landslides.
Another system in the Gulf of Mexico was expected to soon become a tropical storm. The National Hurricane Center said the system has an 80% chance of developing into a tropical disturbance or tropical storm before reaching the western Gulf coastline Tuesday.
Some information for this story came from The Associated Press, Agence France-Presse and Reuters.