The Inland Empire along with the desert and mountain communities saw most of the thunderstorm activity in the afternoon hours.
A flash flood warning was issued until 5:30 p.m. for San Bernardino County, which saw up to an inch of rain, according to the National Weather Service.
Some areas under the warning included San Bernardino, Redlands, Yucaipa, Highland, Running Springs, Highway 18 between Running Springs and Big Bear, Highway 330 between San Bernardino and Running Springs, Angelus Oaks, Highway 18 between Running Springs and Skyforest and Mountain Home Village.
The low desert areas also saw thunderstorm activity, mainly in the area surrounding Palm Springs, just east of Desert Hot Springs and south of Yucca Valley. People living in Redlands and Riverside saw rain coming down around noon.
Concern for mudflows grows after recent SoCal wildfires
After the recent wildfires, there is also concern about debris and mudflows.
The Los Angeles County Sheriff's Department listed the unincorporated communities of Mount Baldy, Wrightwood, Big Pines, Agua Dulce and Santa Maria as "potentially vulnerable locations."
The Bridge, Line and Airport fires are the three largest active wildfires in the state. Combined, they have scorched more than 117,500 acres and destroyed at least 234 structures, but crews have managed to make good progress on the flames.
In the meantime, officials are asking residents to stay away from those recently burned areas, saying flooding at creeks, roads and normally dry arroyos is likely.
"The heavy rains will likely trigger rockslides, mudslides and debris flows in steep terrain, especially in and around these areas," said the NWS.
READ MORE | Concern for mudflows grows as rain slams Southern California amid fight against wildfires