A flash flood warning was issued about 7:15 p.m. Friday for central Los Angeles County as a band of heavy rain centered over the region.
Rain was falling as fast as 1 inch per hour from Sunland-Tujunga to Beverly Hills. Urban flash flooding could occur through the 8 p.m. hour. Lightning was reported in Hollywood.
The warning was sent out via text messages on cellphones around the county.
Concern was also high Friday evening in the foothill cities east of Los Angeles, just under the San Gabriel Mountains, where burned hillsides pose a risk of mudslides.
An unstable hillside in Azusa prompted police to order evacuations of all 26 homes on Ridge View Drive in the Colby fire burn area.
Glendora City Manager Chris Jeffers said sandbags are holding and mud is being funneled onto the streets, but whether the city escapes mudslides depends on the next several hours.
"That could all change as the rain forecasts continue to change," Jeffers said. "Our concern still remains the intensity of the rain. The hills are very damaged ... the vegetation is nearly lost. The soil has been severely damaged, so water just runs off of it."
Assistant L.A. County Fire Chief of Operations Steve Martin said debris flows are starting to pick up and "the mud is getting thicker."
"Now is a very important time for us to be diligent in these patrols," he said.
Martin reminded people to follow the mandatory evacuation orders in Glendora and Azusa because firefighters may be unable to rescue them in an emergency.
"At the risk of sounding coarse … if you are stuck in your house and mud and debris is there, were are not going to come get you out while that debris is still flowing," he said.
As the light rain suddenly became a downpour during a 3 p.m. news conference at the Glendora library, somebody yelled, "That's a microburst, people! That's what we don't want!"
"This could be bad," another agreed.
At an evacuation shelter in Glendora, Mike Schaub clutched the purple leash of his 2-year-old German shepherd, Daisy, and considered what to do.
Schaub had come to the Crowther Teen and Family Center in his black rubber rain boots and ripped jeans after evacuating his home on Cairngrove Lane. The land behind his house was still charred from the Colby fire earlier this year, which came to within about 30 feet of the back of his house.
Now, the charred land is mud, which is slowly sliding down the hill.
"It's the hillside falling down," he said.
With Daisy in tow, Schaub had to decide Friday whether to part ways with his dog. In front of him, a Los Angeles County Animal Control truck waited to receive the German shepherd. Three dogs had already been dropped off by an evacuated woman.
"I can't do it. I can't do it," Schaub told the animal control officers.
Schaub lives with his girlfriend and her daughter, as well as his teenage son. They evacuated Thursday and stayed overnight in Pasadena. Daisy had stayed at the house where she was comfortable, but tonight he would probably leave the dog with relatives, he said.
"The first round wasn't so bad," he said of the rain. But as he was leaving the evacuation center, he looked up at the gray sky and said, "Those drops are getting bigger."
Meanwhile, in Sunset Beach, Alex King shuffled in and out of his 32-foot sport fishing boat. He said this kind of rain was not what he signed up for when he moved south from Seattle 15 years ago.
"I hate the rain," he said. "That's why I live in Southern California."
King, 33, had moved to the Pacific Northwest with his family after the Northridge earthquake destroyed their home. But given his choice, he'd take the quakes.
"Screw the earthquakes," he said. "I'd rather live with earthquakes than rain."
There were more than 150 crashes on Los Angeles County highways Friday morning, up from 46 crashes on the same day the week before.
Across Southern California, there were at least 32,500 customers without power for some part of Friday, including 18,000 Southern California Edison customers and 14,500 with the Los Angeles Department of Water and Power.
There were gusts of up to 39 mph at Los Angeles International Airport and up to 76 mph in the San Gabriel Mountains.