The California Independent System Operator issued a Flex Alert for Thursday from 5 pm. a 10 pm. to help relieve stress on the grid. It asks Californians to set thermostats to 78 degrees or higher, turn off unnecessary lights and avoid the use of major appliances.
Earlier on Wednesday, the agency said the grid was stable and there was no expectation of rotating power outages.
Summerlike heat arrived with spring still on the calendar as a dome of high pressure covered the West. Oppressive daytime highs have been followed by very warm nights.
Palm Springs hit a record 120 degrees on Tuesday, four degrees above the old June 15 record set in 1961.
A coastal eddy swirling low clouds over Southern California brought enough cooling Wednesday for forecasters to reduce some excessive-heat warnings to advisories around the Los Angeles region.
A milky haze of smoke from fires in Arizona, Nuevo Mexico, y México also blew over Southern California, the National Weather Service said.
Excessive-heat warnings were going into effect in the Central Valley, where some locations could see highs up to 113 grados.