The California Independent System Operator issued a Flex Alert for Tuesday, and residents were urged to conserve electricity until 9 p.m.
Southern California has been experiencing hot and humid weather, with temperatures in the upper 90s in the Valley and the Inland Empire.
The alert will be in effect Tuesday and Wednesday, according to the California ISO.
A flex alert is issued when the state's power grid is under stress due to elevated demand or transmission system outages. Officials predicted peak energy demand for the day to hit 44,700 megawatts around 6 p.m.
City News Service contributed to this report.