The National Weather Service reported Torrance received 2.34 inches of rain.
Tito Gonzalez's engineering business was flooded with about a foot of water.
"We're drowning. We had all employees inside here. We couldn't open the door in the front and we couldn't open the gate in the back because we were retaining water at both ends," Gonzalez said.
A flash-flood warning was issued for south central Los Angeles County, including Torrance and west Carson, late in the afternoon and lasted until 6:45 p.m. The rain stopped after a brief cloudburst.
Watches/Warnings --> abc7.la/WxWarnings
Major flooding was reported from 190th to Carson streets between Western and Van Ness avenues in Torrance. Those streets were briefly closed, but reopened by about 6:30 p.m. About five cars were stranded by the rain and were getting help from police and firefighters but there were no reports of injuries or danger to the people inside.
Drivers were urged to avoid the area. Delays were expected.
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The Associated Press contributed to this report.