The California Independent System Operator is asking consumers to conserve electricity Wednesday, especially during the peak demand period between 2 p.m. and 9 p.m.
Cal-ISO says electricity supplies are expected to be tight due to use of air conditioners, power plant outages and reductions in transmission line import capacity due to high temperatures in neighboring states.
The National Weather Service has issued an excessive-heat warning for a vast swath of California's southeastern flank. Heat advisories are posted for the high deserts, Coachella Valley and the Anza Borrego desert.
The coastal region from Los Angeles to San Francisco and most of the state farther north will also be hot.