SAN DIEGO, United States (AP) — Deadly floodwaters inundated streets across Mexico’s arid Baja California on Sunday as Tropical Storm Hilary moved ashore carrying torrential rain into Southern California, and concerns mounted that flash floods could strike in places as far north as Idaho that rarely get such heavy rain.

Forecasters said Hilary was the first tropical storm to hit Southern California in 84 years, bringing the potential for flash floods, mudslides, isolated tornadoes, high winds and power outages.

Hilary made landfall along the Mexican coast in a sparsely populated area about 150 miles (250 kilometers) south of Ensenada, on a path to hit mudslide-prone Tijuana Sunday evening, threatening the improvised homes that cling to hillsides just south of the US border.

At least nine million people were under flash-flood warnings as heavy rain fell across normally sunny Southern California ahead of the brunt of the storm. Desert areas were especially susceptible along with hillsides with wildfire burn scars, forecasters warned.

Mud spilled onto highways, water overwhelmed drainage systems and tree branches fell in places from San Diego to Los Angeles. The weather service said tornadoes were possible Sunday afternoon in eastern San Diego County.

Southern California got another surprise in the afternoon as an earthquake with a preliminary magnitude of 5.1 hit near Ojai, about 80 miles (130 km) northwest of downtown Los Angeles, according to the US Geological Survey. It was felt widely and was followed by smaller aftershocks. There were no immediate reports of major damage or injury, according to a dispatcher with the Ventura County Sheriff’s Office.

Hilary could wallop other Western states with once-in-a-century rains, with a good chance of it becoming the wettest known tropical cyclone to douse Nevada, Oregon and Idaho. Hilary was expected to remain a tropical storm into central Nevada early Monday before dissipating.

By 2:00 pm, California time, Hilary was 115 miles (180 kilometers) south-southeast of San Diego, the National Hurricane Center reported. The storm had maximum sustained winds of 60 mph (95 kph) and was moving northwest at nearly 25 mph (41 kph).

Hurricane Center Director Michael Brennan said that while Hilary had weakened from a Category 4 hurricane, it’s the water, not the wind, that people should watch out for most — some areas could get as much rain in hours that they typically get in a year.

Hilary is just the latest major climate disaster to wreak havoc across the US, Canada and Mexico. Hawaii’s island of Maui is still reeling from a blaze that killed over 100 people and ravaged the historic town of Lahaina, making it the deadliest US wildfire in more than a century. Firefighters in Canada are battling that nation’s worst fire season on record.

The Mexican cities of Ensenada and Tijuana closed all beaches and opened a half-dozen shelters at sports complexes and government offices.

One person drowned Saturday in the Mexican town of Santa Rosalia when a vehicle was swept away by an overflowing stream. Rescue workers saved four other people, said Edith Aguilar Villavicencio, the mayor of Mulege township.