Tropical storm Hilary made landfall over the Baja California peninsula on Sunday, pelting the region with intense rain and heading toward the US Southwest, where forecasters warned of life-threatening and “catastrophic” flooding.

One person died in Mexico amid reports of flash flooding in the peninsula, where some roads were swept away and images on social media showed raging torrents gushing down city streets that have been turned into rivers.

In the United States, the storm has already wreaked havoc on flights and sporting events before it even arrived, while officials warned residents to remain indoors and keep emergency supplies handy.

Though Hilary had been weakening over the last 48 hours as it neared land, it is still set to be the wettest storm ever to hit the US Southwest, according to Zack Taylor, a meteorologist with the National Weather Service (NWS).

“This is a dangerous storm,” said Taylor, who works for NWS’s Weather Prediction Center in College Park, Maryland. “It’s not just the rain totals but the intensity.”

Hilary is set to dump vast amounts of water on many parts of the US Southwest that are more accustomed to dry conditions.

Areas such as Palm Springs, California, which typically gets around 4.6 inches of rain in an entire year, could receive 6-10 inches from this one storm.

California’s Death Valley area, which receives only about 2.2 inches of rain per year, could receive three to four inches from this event.

Hilary made landfall on Sunday morning over the northern parts of the Baja California peninsula, the National Hurricane Center (NHC) said in its latest advisory.

The storm was carrying top sustained winds of 60 mph (96 kph) and its centre was forecast to barrel over the northern portion of the peninsula and then move across Southern California on Sunday afternoon.

Storm surges — when the ocean is pushed inland — could produce coastal flooding in parts of Baja California and the storm was carrying heavy rain that could cause catastrophic flooding in some areas, the NHC added.

Rainfall of three to six inches, with isolated amounts of 10 inches, was expected across the northern Baja California peninsula as well as portions of Southern California and Southern Nevada, the Miami-based agency said in its latest advisory.

As of 2 pm EDT, Hilary was about 215 miles south-southeast of San Diego, California, the forecaster said. It was moving north-northwest at 25 mph.

Los Angeles Mayor Karen Bass urged residents across the second-most populous US city to stay home as the storm passes.

“Avoid unnecessary travel. If you don’t need to be on the road, please do not get in your car,” she said at a press conference on Sunday.

Los Angeles Fire Department Chief Kristin Crowley said the city has staffed additional fire engines and several swift-water teams in case flood rescues are needed. Urban search and rescue teams have also been deployed throughout the city along with helicopter teams to assist in rescues from the air.

It has been seven decades since the last tropical storm made landfall in California. In September 1939, the Long Beach tropical storm killed almost 100 people.

Mexico evacuations

In Mexico, nearly 1,900 people have been evacuated to shelters in the Baja California peninsula, according to the country’s army.

Schools and other nonessential activities were cancelled through Monday, and authorities in the city of Tijuana, bordering San Diego, urged people in high-risk zones to move to temporary shelters.

Around the coastal town of Mulege, on the eastern side of the Baja California peninsula, one person died after his family was swept away while crossing a stream on Saturday.

Phone lines and electricity were cut in several of the surrounding villages after lamp posts fell, the Mexican army added.

Mexico’s Navy also evacuated about 850 people from five islands in the path of Hilary, which was previously designated a Category 4 hurricane before it weakened.

Many businesses in the US were also taking severe precautions.

About 250 flights scheduled for Sunday at the San Diego International Airport have been cancelled and another 364 on Monday, according to the FlightAware website.

In California, Major League Baseball’s Los Angeles-based Dodgers and Angels brought their Sunday games forward to Saturday to turn them into split doubleheaders.

The city’s soccer teams, Los Angeles FC and LA Galaxy, both postponed their Sunday matches due to threat of heavy rains and flooding.