The fast-moving downpour happened at about 11 p.m., triggering the mudslide. It lasted only 15 to 20 minutes, but it was enough to send mud cascading over the K-rails.
Crews have been working for several hours to clean the muddy mess in neighborhoods.
On Rock Castle Road, mud poured into streets, but fortunately, where the mud came down was right on a curb, where there are no homes directly in the path of the mudslide.
Battalion Chief Steve Martin from the L.A. County Fire Department said about a dozen homes were damaged, as well as a few cars.
"When I was first drove up here, I was running into boulders the size of soccer balls," Martin said.
Crews estimated about 40 to 50 tons of mud poured onto the road.
L.A. County Fire crews said a handful of residents heard the hillsides begin to give way and left their homes on their own. They have since returned, and nobody was injured. There are no evacuation orders in place currently.
Rock Castle Road has been closed while crews work to clean the mess.
Martin said when the rain comes, officials will be issuing evacuation orders.
"This isn't like a fire, where some of us can stay and some can go," Martin said. "This is not something that we can come up here and work in, and it's not something you can live through."