The alert will be in effect today and Wednesday, according to the California Independent System Operator.
"Consumers are urged to reduce their energy use during the late afternoon when air conditioners drive consumption to the highest point of the day," according to the alert.
According to Cal-ISO, a flex alert is issued when the state's power grid is under stress due to elevated demand or transmission system outages. The alerts call for voluntary conservation so the state will not have to dip into energy reserves.
Cal-ISO predicted peak energy demand for the day to hit 44,700 megawatts around 6 p.m.
The agency offered a series of tips for conserving energy: