Southern California residents are being asked to conserve energy for a fourth consecutive day Saturday amid the summer’s longest heat wave.

The California Independent System Operator (ISO) issued a Flex Alert from 4 p.m. to 9 p.m. due to increasing high heat, tightened energy supplies and more potential strain on the grid.

The Flex Alert is the fourth consecutive call on residents to conserve energy as the power grid operator is again expecting high electricity demand throughout the Labor Day weekend and into next week, primary due to air conditioning use, Cal Iso stated in a news release.

Southern California is currently in the midst of a record-breaking heat wave that isn’t expected to end any time soon.

Scorching temperatures are forecast to continue through Wednesday of next week, according to the National Weather Service.

Daytime highs between 95 and 113 degrees are possible in some of the hottest areas with Sunday likely to be the hottest day, the Weather Service stated.

Preliminary data show that conservation during the Flex Alert hours has been helpful in keeping the grid stable so far this week, Cal Iso stated.

Californians are urged to set thermostats to 78 degrees or higher, avoid using major appliances and turn off all unnecessary lights between 4 and 9 p.m.

Consumers are also encouraged to pre-cool their homes and use major appliances before 4 p.m.

For more information on Flex Alerts, go to FlexAlert.org.