A large swath of California was bracing Thursday for an intense bout of rain that could lead to flooding and cause debris flows in areas recently burned by wildfires.

The Southern California regions scorched by flames last month were of particular concern because the soil in those areas can repel water and allow sheets of water to race downhill, collecting debris along the way.

In the Los Angeles area, about two inches of rain was expected over the next two days, but some parts of Southern California could receive more than four inches, according to the National Weather Service office in Oxnard, Calif. A torrent of rain within a short period could pose particular problems.

“It’s looking like we’re going to be seeing the highest amount of rain that we’ve had in a single storm so far this season,” Lisa Phillips, a meteorologist with the Weather Service, said.

Some officials in Southern California began to issue evacuation warnings and orders on Wednesday. In Santa Barbara County, the sheriff’s office ordered evacuations in areas in and around the burn scar of the Lake fire, which burned more than 38,000 acres last year. Residents under the order were told to leave by 3 p.m. on Wednesday, and those who chose not to evacuate were told to prepare to sustain themselves for several days if they had to shelter in place.

In Los Angeles County, an evacuation warning was issued for areas recently affected by the Palisades fire, which burned more than 23,000 acres. Los Angeles Fire Department officials said that there was a high risk of landslides in the area.

Sheriff Robert Luna of Los Angeles County said at a news conference on Wednesday that officials had been notifying residents in areas with elevated risk, and he urged residents to heed to any evacuation orders they received.

“Storms can bring sudden and severe conditions that make staying back home extremely risky,” Sheriff Luna said. “Do not take that chance.”

Landslides could prevent law enforcement personnel and emergency crews from being able to reach those in need, Sheriff Luna added.

Concerns this week extended beyond areas affected by the Palisades and Eaton fires. Mark Pestrella, the director of the Los Angeles County Public Works Department, said on Wednesday that any burn scar area from a fire within the past year could be at risk. In Orange County, the Sheriff’s Department issued an evacuation warning near the site of the Airport fire, which burned more than 20,000 acres in the foothills of the Santa Ana Mountains. In Malibu, all public schools were closed on Thursday because of the storm.

To prepare for the heavy rain, the California Governor’s Office of Emergency Services said that it had positioned resources across 14 counties, from Sonoma County in Northern California to San Diego County at the southern border. Intense storms were also being forecast Thursday in the Bay Area and other parts of Northern California, but they were not expected to cause as many problems as in Southern California.

Officials in Santa Barbara County, which experienced a deadly mudslide in 2018 along with flooding in recent years, have been preparing for the storm since late last week, said Jackie Ruiz, a spokeswoman for the county’s emergency management office.

Residents have been picking up sandbags at filling centers throughout the county, she said.

“We had back-to-back years of pretty intense rain here,” Ms. Ruiz said, “so it’s something that we’re very familiar with in the community.”

On Wednesday, sheriff’s deputies were knocking on the doors of about 50 properties within the burn scar area of the Lake fire, Ms. Ruiz said. Officials were also trying to reach people who live in encampments in creek beds, underpasses and other places that are prone to flooding, she said.

In San Luis Obispo County on the Central Coast, officials were preparing for possible flooding as severe as what occurred in January 2023, when heavy rainfall inundated communities. During that storm, a 5-year-old boy was swept away and killed when floodwaters overwhelmed his mother’s vehicle.

Local agencies were increasing staffing and positioning emergency resources, said Anita Konopa, the emergency services coordinator for San Luis Obispo County. They were also working with the American Red Cross to identify potential evacuation shelters.

Jonathan Wolfe contributed reporting.