FOLSOM (CBS SF) — A statewide Flex Alert issued by the California Independent System Operator (ISO) has been extended into Saturday, with officials calling for conservation as extreme heat raises demands on the state’s power grid.

The Flex Alert announced Thursday that went into effect Friday afternoon was originally covering 4 p.m. to 9 p.m. The Cal ISO announced the extension of the Flex Alert to also cover the same time period starting Saturday afternoon.

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A tweet announcing the extended Flex Alert also noted that the large wildfire in Southern Oregon was threatening transmission lines, creating greater strain on the power grid.

The Flex Alert is part of Cal ISO declaring a State 1 Power Grid Emergency. Officials said that rolling blackouts are not currently part of the plan to cope with the strain on the grid; blackouts do not happen until the state hits a Stage 3 Power Grid Emergency.

“When they know that the supply is going to be tighter than expected, when they know that peak demand for energy use between the hours of four and nine pm is going to go up because of the heat. They call for rotating outages when the supply just doesn’t meet that demand and right now there’s no indication that they will call for rotating outages,” said Pacific Gas and Electric spokesperson Deanna Contreras.

PG&E says conserving power can be done easily if you plan ahead.

“Pre-cooling your home really helps a lot. Keep your blinds down, run the air conditioners before 4 p.m., cool down the house and that will help when it gets hotter and the temperatures go up later on,” explained Contreras.

The extension of the Flex Alert into Saturday comes hours after an Excessive Heat Warning covering much of the Bay Area also went into effect as temperatures soared in much of the region.

“Dangerously hot conditions with daytime temperatures of 102 to 110 expected,” the weather service said in a statement, with some isolated areas possibly reaching higher temperatures. Overnight hours are expected to provide little relief, as temperatures are only expected to dip into the 70s and 80s.

The National Weather Service issued the Excessive Heat Warning for most inland areas in the North Bay and East Bay, along with the Santa Cruz Mountains from noon on Friday through 11 p.m. Sunday.

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“Such conservation would help ease the strain on the grid during the crucial evening hours when solar energy is diminished or no longer available,” the release issued by Cal ISO on Thursday said.

The release noted the success of past Flex Alerts — both last month as temperatures spiked in mid-June heat wave and during last summer’s regional heat wave — when consumers collectively reduced their energy use significantly. That allowed grid operators to avoid or limit possible rotating power outages that can become necessary when demand for electricity outstrips capacity.

Among the specific actions consumers can take to reduce energy consumption during the Flex Alert are:

  • Set thermostats to 78 degrees or higher, if your health permits
  • Avoid using major appliances, like dish washers and clothes washers and dryers
  • Turn off all unnecessary lights

Consumers are also encouraged to use fans for cooling and unplug unused electrical items.

In the hours prior to the Flex Alert taking effect, consumers were advised to take the following steps to help the state manage energy use later in the day:

  • Pre-cool your home by lowering the thermostat
  • If you need to use your major appliances, do it earlier in the day, when solar energy is abundant
  • Close window coverings to keep your home or apartment cool
  • Take advantage of the solar energy to charge electronic devices and electric vehicles so there’s no need to do it later, when solar is not available

The above steps can also help people be more comfortable when cutting back on their electricity usage.

Now that the Flex Alert is in effect, if demand continues to outstrip supply, the Cal ISO will use other tools it has available for emergency conditions until those options are exhausted. The ISO could order California utilities to reduce demand by implementing rotating power outages of short duration to effectively extend the available electricity as much as possible.

On Thursday, Cal ISO said it was not anticipated that rotating outages would be needed. As California’s ability to store solar and wind energy with batteries or other technology continues to improve, those crucial evening hours will be less of a challenge and similar emergencies rarer.

For information on Flex Alerts, and to get more electricity conservation tips, visit the Cal ISO’s Flex Alert website.

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Andria Borba contributed to this story.