A southerly swell has brought dangerous rip currents to the water from San Diego to Oxnard, and the heavy surf is forecast to become most intense on Monday as thousands flock to the beach on the final day of the holiday weekend.
"Make sure you don't get knocked off. When you are in the surf zone, you can be swept off your feet and pulled out to sea," Kaplan said.
If caught in a rip current, he advised swimming in a parallel direction to the shore until the pull relents.
The swell, which originates from several storm systems south of the equator, was expected to peak Monday afternoon. Forecasters could extend a beach hazards statement until Tuesday because of lingering rip currents, Kaplan said.
Coastal temperatures Monday are expected to remain "cooler than normal," with highs in the high 60s to mid 70s, Kaplan said. Parts of the San Fernando and Antelope valleys are expected to reach the high 70s, according to the weather service.
Southern California will warm up by Wednesday, with the valleys reaching the mid-80s on Thursday and Friday.