San Francisco, Aug 16 (IANS): Due to a continuing heatwave in California, authorities have declared Stage 3 Electrical Emergency, initiating phased power outages throughout the state for the first time since 2001.

On Saturday, residents in many counties in Southern California, including Los Angeles, Orange and Ventura, lashed out at the California Independent System Operator (Cal ISO), which manages the power load, after it declared the emergency measure on Friday to maintain the stability of power system, reports Xinhua news agency.

Los Angeles County is the most populous county in the US, with more than 10 million inhabitants as of 2018 and the Los Angeles metropolitan area is estimated to have a population of nearly 20 million residents.

Authorities in Southern California cities said they suffered blackout varying between 15 minutes and 1 houron Friday night.

Also on Friday, Cal ISO issued a statewide flex alert, under which Californians are being urged to turn off unnecessary lights, use major appliance before 3 p.m. and after 10 p.m., and set their air conditioner thermostats to 25.5 degrees Celsius or higher.

"California will be experiencing near-record or record-breaking heat, up to 10-20 degrees above normal in some areas," ISO said in a statement, adding it tried to manage the strain on the grid to limit any potential power disruptions.

Excessive heat warnings were issued by National Weather Service on Saturday morning and will be in effect till next Wednesday for most of the Southern California.

High temperatures are forecast for the Inland Empire, Orange County, the Ventura County coasts and valleys, and could reach as high as 48.9 degrees Celsiu) in the low deserts.