(CNN) - Another round of heavy rain was hitting California on Wednesday, putting millions of people under a flash-flood watch and spurring precautionary evacuations in several wildfire-scarred areas vulnerable to mudflows.
In what should be the strongest in a series of recent storms, up to 3 inches of rain are expected in Southern California through Thursday and 6 inches could fall in central portions of the state. The heavy rain was expected to roll in Wednesday evening.
The rain could lead to mudflows and flooding in areas burned by wildfires last year.
Nearly 15 million people were under a flash-flood watch Wednesday morning from the Los Angeles area to central and northern parts of the state, the National Weather Service said.
Evacuations and closures
Among the wildfire-scarred areas watching particularly closely for mudflows:
• Los Angeles County: Evacuations have been ordered for several communities with steep slopes deemed at risk for mudslides, especially after last year's Woolsey Fire scorched the area. Evacuation centers have been opened in Santa Monica and Agoura.
Schools in the seaside town of Malibu, which was hit by last year's fires, were closed Wednesday as a precaution.
"You can't outrun or fight these mudslides," Malibu Mayor Jefferson Wagner said in a video message Tuesday urging people to follow evacuation orders. "Stay cautious, stay dry, and let's get through this next event without issue."
Rainfall is expected to increase by noon Wednesday in Southern California "and become heavier in the evening and overnight," the National Weather Service said.
• Ventura County: Mandatory evacuations were issued Tuesday for parts of this county west of Los Angeles, including its south coast and the Matilija and Wheeler Springs areas.
"(The rain) may cause significant debris flows and flooding in the recent burn areas," the county's emergency information website reads. "In addition, some rockslides can be expected along canyon roadways outside the burn areas."
• Butte County: The sheriff's office in this Northern California county urged evacuations in the town of Pulga, about a 100-mile drive north of Sacramento, from Tuesday night into Thursday morning.
"If flooding occurs, this can quickly become a dangerous and life-threatening situation," the sheriff's office said.
Parts of the county were burned last fall by the Camp Fire, the state's most deadly and destructive wildfire on record.
Strong winds and heavy snow, too
Wednesday's storms also are expected to bring strong winds to central and northern parts of California, including San Francisco. Wind gusts could reach around 60 mph.
The storms also will bring snow -- up to 6 feet -- to parts of the Sierra Nevada. A blizzard warning is in effect into Thursday morning for elevations above 6,500 feet.
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