DIAMOND BAR, Calif. − Historic Hurricane Hilary was churning toward the Pacific Coast early Sunday as Southern California braced for up to 10 inches of rain and “dangerous to catastrophic” flooding, the National Weather Service warned.

Maximum sustained winds were near 80 mph with higher gusts, and Hilary was forecast to remain a hurricane as it passed the Baja California Peninsula south of San Diego. Hilary, though expected to weaken to a tropical storm as it rolls north toward Southern California, still threatened to devastate a swath of the U.S. Southwest with heavy rainfall through Monday morning.

The storm, centered about 285 south-southeast of San Diego at 8 a.m. ET, was poised to make history as the first tropical storm to slam Southern California in 84 years. Flash floods, mudslides, isolated tornadoes, high winds and power outages were possible.

In Diamond Bar, a city of 55,000 residents 20 miles east of downtown Los Angeles, locals raced to the city’s three fire departments Saturday in an ill-fated effort to score sandbags desperately needed to protect their home from the storm. But people had begun filling up bags of sand on Friday, and officials said one station ran out within an hour.

On Saturday, one station in the west side of the city got two shipments of sand, but it went out as fast as it came in, according to Los Angeles County Fire captain Jesse Vasquez.

“We’re bombarded,” Vasquez told USA TODAY.” It was nonstop. We got depleted.”

Forecast developments:

∎ Rainfall amounts of 3 to 6 inches, with isolated amounts of 10 inches, were expected across portions of southern California and southern Nevada, where flooding could be most severe.

∎ California Gov. Gavin Newsom proclaimed a state of emergency, and authorities issued an evacuation advisory for Santa Catalina Island, 23 miles off the coast.

∎ As the storm rolls north, portions of Oregon and Idaho could see as much as 3 to 5 inches of rain, producing some “significant” flash flooding, the weather service said.

Sandbags hard to find as storm approaches

Vasquez said many people who picked up sandbags from the stations were panicking, taking more than they could possibly need.

“We can’t go out there and argue with them,” he said. “We can educate and ask and plead with them. But at that point, they’re gonna do whatever they want to do.”

Fire stations were getting over 300 calls Saturday asking where to get sand, and instead were giving people tips on how to prepare for any dangerous weather, such as boarding up houses and covering any possible cracks or holes. The demand for sand has been so high, Vasquez said, some residents told him they were driving to beaches to fill up bags.

All fire stations – operated by Los Angeles County – will be fully staffed with more equipment than normal in the city Sunday, Vasquez said, but they know depending on the intensity of the weather, it might be a difficult task to come to the aid of residents as they try to evacuate anyone severely impacted. In a city with so many hills, mudslides will also be something firefighters have to consider possibly occurring.

“The department is prepared. We have the manpower and staff, but we’re just sitting there, waiting for it, to see what happens,” he said. “We do our best to protect life and property. That’s our main objective.”

Fire officials aren’t sure if they will get another delivery of sand from the city on Sunday morning, when the storm is expected to arrive in the area. Officials in nearby Pomona said the city ran out of sandbags Saturday night but is expecting to get more Sunday morning.

Palm Springs braces for flooding

Farther inland in Riverside California, weather service meteorologist Elizabeth Adams said rain could fall up to 3 inches an hour Sunday near Palm Springs across the desert and mountains surrounding the Coachella Valley. The intense rainfall during those hours could cause widespread and life-threatening flash floods, Adams said.

National Weather Service placed the Coachella Valley under a tropical storm warning, emphasizing the potential for high winds and extreme flooding rain that “may prompt numerous evacuations and rescues.” Palm Springs Fire Chief Paul Alvarado urged residents not to ignore barricades and other warnings on local roads.