The operator of California's power grid has asked people to conserve energy for the sixth day in a row as the state swelters in record-breaking temperatures.
The California Independent System Operator (ISO) said there could be rolling blackouts in the state if the guidance in the "flex alerts" isn't followed.
During a flex alert, consumers are urged to reduce their energy use in the afternoon and evening hours when the grid is most stressed because of high demand.
People have been asked to use less power between 4pm and 10pm local time on Monday (midnight and 6am UK time on Tuesday) under the latest alert.
The California ISO had earlier asked people to use less energy between 4pm and 9pm local time on Saturday and Sunday as demand spiked and temperatures were still on the rise.
People are urged to save power during flex alert periods by setting their thermostats to 78F (25C) or higher, not using major appliances such as dishwashers and washing machines, and turning off unnecessary lights.
Speaking at a news conference when alerts were announced for Saturday and Sunday, the California ISO's president Elliot Mainzer said: "When we're in a situation like this, where we're right up against the margin of system capability and you have the kinds of threats to reliability from fires and generation plants coming offline, that consumer flexible demand, that response, can be the difference between the lights staying on or not."
The latest alert comes after multiple generators were forced out of service due to extreme temperatures in the state, the Los Angeles Times reports.
Meanwhile, the California ISO has warned ongoing wildfires and potential new blazes could further strain the power grid by crippling lines and further generators.
"Sunday, Monday, and Tuesday in particular are shaping up to be the most difficult of this heat wave," the agency said in a news release.
The National Weather Service has warned temperatures in California could reach 115F (46C) by the middle of the week.
It comes after the southern California city of San Diego sweltered in a record temperature of 95F (35C) on Saturday.
Meanwhile, firefighters in Northern California's Siskiyou County have been battling a fire which has left two people dead and caused thousands to evacuate their homes.