Near the border with Mexico, the high at Campo was 100. The previous record was 95, set in 1984, according to the National Weather Service.
Along the coast, temperatures were in the mid-70s.
Bob Hope Airport in Burbank topped out at 103 degrees, breaking a 100-degree record for the day that had stood since 1976, the NWS said. Lancaster recorded 98, topping by one degree the record set in 1996.
The warm weather was a result of high pressure over the region, the Weather Service said.
Temperatures were expected to be about 10 degrees cooler across the area Tuesday as onshore winds from the coast blow across the region.