FOLSOM (CBS SF) — A heat wave in the forecast for Northern California has prompted a statewide Flex Alert for Wednesday evening. The California Independent System Operator (ISO) is asking residents to conserve electricity from 4 p.m to 9 p.m., to reduce the strain on the state’s power grid.

Rate payers and consumers should turn off unnecessary lights, and delay using major appliances during that time. They should also set the thermostat on their air conditioners to 78 degrees or higher.

For more conservation tips visit FlexAlert.org.