A flash flood watch was in effect for the Los Angeles County mountains and Antelope Valley through Sunday evening as rain began to move into the drought-stricken region Saturday night.
Moonsoon moisture moving into the region was expected to bring an increased risk of slow-moving thunderstorms and flash flooding in those areas, excluding the Santa monica range, the National Weather Service said.
By Saturday late night, scattered rain was coming down on the Westside to the Inland Empire after the system moved in from San Diego.
The thunderstorms may produce rainfall rates of 1 inch per hour, the NWS said.
Authorities were preparing for another round of thunderstorms at Southern California beaches this weekend as forecasters predict same cloudy conditions like last weekend when a man died after being struck by lightning.
Although the conditions which killed a 20-year-old swimmer at Venice Beach last week are extremely rare, there is a chance of them on Sunday.
"We're working on an effective way to clear the beach,"said Chris Linkletter, a Los Angeles County lifeguard.
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Southern Californians, not used to weather, are complacent when it comes to lightning, so many people may not get out of the water when they hear thunder, Linkletter said
"If you can hear thunder and, obviously, see lightning, no place outside is safe," Linkletter said.
Linkletter has met with weather forecasters to plan for weekend storms with the hope of keeping beachgoers safe. Thousands of people flock to Southern California beaches every weekend and lifeguards face a tall order trying to clear everyone out of the water.
There is no public announcement system in place to help communicate in emergencies.
Forecasters predict a slight chance of showers and thunderstorms overnight Saturday and early Sunday along the coast in Orange County and Los Angeles with temperatures ranging from 74 to 79 degrees.
Molly Sullivan was at Venice Beach Sunday when 20-year-old Jay Fagnano was fatally struck by lightning. Thirteen others were injured.
Fagnano had stepped into the water to wash off sand to get ready to leave when lightning struck, family members said.
With the looming threat of another storm this weekend, Sullivan's thinking twice about another beach trip.
"It's terrifying," she said, digging a hole with her boyfriend in the sand at Zuma Beach in Malibu on Friday. "We watched on the news and it was, like, 'Wow, that could have been us.'"