California’s electric grid operator issued an active notice to power companies on Wednesday, asking them to restrict maintenance operations on the power grid for most of the day as the state continues to sizzle through a heat wave.

The California Independent System Operator (CAISO) warned that it “anticipates generation resources may be inadequate” for the duration of the notice, which took effect at 6:00 a.m. and continues to 10:00 p.m. Pacific Time. The grid operator also cautioned market participants “to avoid actions which may jeopardize generator availability.”

CAISO forecast that peak demand would reach 45,786 MW on Wednesday, followed by 46,888 MW on Thursday. Those demand levels are hovering around last summer’s peak load of 46,257 MW (see Daily GPI, Sept. 10, 2015). The grid operator registered a record all-time peak load of 50,270 MW on July 24, 2006 during a regional heat storm (see Daily GPI, Aug. 25, 2006).

By Wednesday afternoon, CAISO issued a flex alert, an urgent call for consumers to cut back on electricity and shift demand to off-peak hours, typically after 9 p.m.

Pacific Gas and Electric Co. (PG&E) issued three alerts, one of which was a heat advisory stating that “extreme heat is expected in many areas.” A second alert warned customers that a peak day pricing surcharge would be in effect on Tuesday and Wednesday — with electricity rates hitting $0.849/kWh from 2 p.m. to 6 p.m. A third alert advised customers on methods to keep electricity usage down during the heat wave.

According to AccuWeather Inc., triple-digit temperatures are expected to bake California’s Central Valley into the weekend. New record high temperatures in Sacramento, Redding and Fresno could be set during the heat wave.