Thousands of residents were without power Saturday due to a summer storm that produced heavy downpours, hundreds of lightning strikes and flooding in Southern California.

Lightning strikes prompted the temporary closure of beaches from Long Beach to Zuma. Beaches were closed shortly after 8 a.m. and reopened just before 10 a.m. A second closure of LA County beaches was issued just after 2 p.m.

More than 10,000 Department of Water and Power customers in Los Angeles were left without electricity as a result of the storm, said Kim Hughes, a DWP spokeswoman.

NBC4's Shanna Mendiola said that 4- to 7-foot waves were possible at Southern California beaches, along with dangerous rip currents.

"Our weekend weather will be heavily influenced by Tropical Storm Dolores," Mendiola said. "We will also see high surf at our beaches and an increase in our humidity."

The National Weather Service issued the following watches and warnings:

A flash flood watch was in effect until 8:15 p.m. for the Ventura and Los Angeles county mountains, excluding the Santa Monica range, the Antelope V alley and southeastern San Bernardino County.

A severe thunderstorm watch was in effect until 9 p.m. for Riverside and San Bernardino counties.

A flood advisory for Los Angeles and Ventura counties was in effect until 6:15 p.m.

Tropical Storm Dolores brought a strong swell of warm and muggy weather from the south, spreading monsoonal moisture through Los Angeles and into the San Gabriel Valley and Orange County.