PALM DESERT, Calif. (AP) — Hilary, the first tropical storm to hit Southern California in 84 years, swept people into swollen rivers, toppled trees onto homes and flooded roadways as the massive system marched northward Monday, prompting flood watches and warnings in more than a half dozen states.

The National Hurricane Center in Miami said Hilary had lost much of its steam and only vestiges of the storm were heading over the Rocky Mountains, but warned that “continued life-threatening and locally catastrophic flooding” was expected over portions of the southwestern U.S., following record-breaking rainfall.

Hilary first slammed into Mexico’s arid Baja California Peninsula as a hurricane, causing one death and widespread flooding before becoming a tropical storm, one of several potentially catastrophic natural events affecting California on Sunday. Besides the tropical storm, which produced tornado warnings, there were wildfires and a moderate earthquake north of Los Angeles. So far, no deaths, serious injuries or extreme damages have been reported in the state, though officials warned that risks remain, especially in the mountainous regions where the wet hillsides could unleash mudslides.

In the San Bernardino Mountains, east of Los Angeles, crews were working to clear mud that has been blocking the homes of about 800 residents, said Cal Fire Battalion Chief Alison Hesterly.

Residents also pitched in. In the mountain community of Oak Glen, Brooke Horspool helped dig out a home surrounded by about 4 feet (1.2 meters) of mud to free a couple, including an older man with medical issues.

Amid the storm Sunday in Palm Desert, Terry Flanigan heard a huge crash and then got a text from a neighbor that a Eucalyptus tree, more than 100 feet (30 meters) tall, fell onto a condo across the street. She later learned it landed on the bed of her neighbor’s 11-year-old son, who luckily was in another room.

“It was very unnerving,” Flanigan said, adding that the family had gone to stay with relatives while removal crews came Monday morning to remove the branches. “Oh my gosh, what could have happened.”

Maura Taura felt a similar relief after a three-story-tall tree crashed down on her daughter’s two cars but missed the family’s house in the Sun Valley area of Los Angeles.

“Thank God my family is OK,” she said.

Hilary is just the latest major weather event 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.

Hot water and hot air were both crucial factors that enabled Hilary’s rapid growth — steering it on an unusual but not quite unprecedented path that dumped 10 months of rain in just one day in some normally bone-dry places.

Death Valley National Park received a full year’s worth of rain in one day, and remained closed indefinitely. About 400 people were being sheltered at Furnace Creek, Stovepipe Wells, and Panamint Springs until roads could be made passable, park officials said.

Rain came in two bursts on Sunday — in the morning and evening — totaling 2.2 inches (5.6 centimeters) at a National Weather Service rain gauge at Furnace Creek. If verified, it would be the single-rainiest day in the area’s history, beating its record of 1.7 inches (4.3 centimeters) set Aug. 5, 2022.

Park officials responded Monday to sewer line damage releasing raw sewage into the desert below Stovepipe Wells.

“If a storm is larger, it’s going to rain longer” and over more places, said MIT hurricane scientist Kerry Emanuel.

Scientists still don’t know why some storms, like Hilary, get big and some stay small, he said.

“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.

Sunday was the wettest day on record in San Diego with 1.82 inches (4.6 centimeters), the NWS said in a post on X, formerly known as Twitter. The previous record was on Aug. 17, 1977, when 1.8 inches (4.5 centimeters) of rain fell in the area post-Hurricane Doreen.

“We basically blew all of our previous rainfall records out of the water,” National Weather Service meteorologist Elizabeth Adams in San Diego told The Associated Press.

The wet weather might stave off wildfires for a few weeks in Southern California and in parts of the Sierra Nevada but widespread rain is not expected in the most fire-prone areas, University of California, Los Angeles, climate scientist Daniel Swain said in an online briefing Monday.

The water rose knee-high in a homeless encampment along the rising San Diego River where fire officials rescued 13 people. Farther north, crews pumped floodwaters out of the emergency room at Eisenhower Medical Center in Rancho Mirage.

In Cathedral City in the desert, Kimberly Garnica, 20, woke up to find that her car was stuck in mud outside her home.

“You can just tell the streets aren’t really built for this,” she said.

In the Coachella Valley city of Desert Hot Springs, Steven Michael Chacon said the roads in the housing development where he and his husband live were impassable due to flooding and he was concerned emergency crews might not be able to reach people.

“Basically everybody’s got to stay put, there’s no way in or out,” he said Monday morning.

The center of Hilary passed over downtown Los Angeles at 7 p.m. Sunday, according to the regional weather office, which called it “a day for the ages” in Southern California.

“Los Angeles was tested but we came through it, and we came through it with minimal impacts considering what we endured,” City Council President Paul Krekorian said.

A tropical storm last roared into California in September 1939, ripping apart train tracks, tearing houses from their foundations and capsizing many boats. Nearly 100 people were killed on land and at sea.

As Hilary moved east into the neighboring state of Nevada, flooding was reported, power was out and a boil-water order was issued for about 400 households in the Mount Charleston area, where the only road in and out was washed out. The area is about 40 miles (64 kilometers) west of Las Vegas.

Forecasters said the threat for flooding in states farther north on Monday was highest across much of southeastern Oregon into the west-central mountains of Idaho. The forecast calls for potential thunderstorms and localized torrential rains on Tuesday, said Jackson Macfarlane, a meteorologist with the weather service in Boise, Idaho.

In the Caribbean, meanwhile, Tropical Storm Franklin churned on Monday near Haiti and the Dominican Republic, while forecasters at the National Hurricane Center said another storm could develop and reach the Gulf of Mexico coastline on Tuesday.

Antczak and Stefanie Dazio reported from Los Angeles and Watson from San Diego. Associated Press reporters Ken Ritter in Las Vegas; Will Weissert in Washington; Freida Frisaro in Fort Lauderdale, Florida; Curt Anderson in St. Petersburg, Florida; Eugene Garcia in San Diego; Ryan Sun and Walter Berry in Phoenix, contributed to this report.