SACRAMENTO (BLOOMBERG) - As many as nine million Californians could lose power Sunday (Sept 6) in the biggest rolling blackouts in state history.

The state's grid operator said it may need to impose rotating outages this evening as record-breaking heat pushes the electric grid to the brink.

Uncontrolled wildfires have already cut electricity to almost 70,000 customers in Southern California, downing power plants and transmission lines.

The California Independent System Operator, which runs most of the state's grid, declared a Level 2 emergency - the last step before ordering power cuts.

The crisis comes just three weeks after an August heat wave triggered California's first rotating blackouts since the 2001 energy crisis and fuelled hundreds of wildfires across the state.

As climate change contributes to more extreme weather, the region's heat, wildfire and blackout woes are only getting worse.

UNPRECEDENTED HEAT

The heat gripping the state is unprecedented.

San Francisco hit 38 deg C Sunday, smashing a prior record of 33 set in 1904, according to the National Weather Service. Los Angeles reached 43 and San Diego topped 37, also records.

The Department of Energy earlier issued an emergency order allowing several more power plants to produce as much electricity as possible over the next seven days, even if doing so would otherwise violate anti-pollution rules.

In the meantime, wildfires are wreaking havoc on the grid.

The Creek Fire in the Sierra Nevada Mountains has scorched 45,500 acres and has not been contained.

More than 200 people were airlifted Sunday from a popular camping area in the region.

Yesterday, the blaze knocked out transmission from a hydro plant, while a fire in Southern California cut off a solar farm, the California ISO said.

Together, the blazes sucked 1.6 gigawatts from the power system, enough to power 1.2 million homes.

About half of that had been re-connected by midday Sunday - and then another fire in Southern California cut out 500-600 megawatts.

Wholesale electricity prices in the southern part of the state earlier spiked to the highest level in nearly a year, diverging sharply from prices in Northern California.

At the state grid operator's request, the Energy Department said it was authoriSing power plants in the City of Industry, El Segundo and Long Beach to run at their maximum output levels - even though it may unleash additional air pollution.

In a statement, agency spokesman Shaylyn Hynes said California policymakers should "evaluate why the grid is not able to handle extreme stress, which could be alleviated with the support of greater baseload power generation and natural gas supply."

One thing that has made California's grid so vulnerable to soaring demand is the state's rapid shift away from natural gas.

About 9 gigawatts of gas generation, enough to power 6.8 million homes, have been retired over the past five years as the state turns increasingly to renewables, according to BloombergNEF.

That leaves fewer options when the sun sets and solar production wanes. The state's utilities have commissioned large battery packs to pick up the slack, but most of the batteries haven't been installed yet.

SHUT-OFFS

The Los Angeles Department of Water and Power reported Sunday that some of those who lost power could be without it for 36 hours.

Some of LADWP's equipment was running at 200 per cent of capacity due to the extreme demand for power, and the high night-time temperatures weren't letting the gear cool off.

Utility giant PG&E Corp which powers much of Northern and Central California, warned on Saturday that it may decide to cut power to about 103,000 customers in parts of the San Francisco Bay area and Sierra Nevada foothills starting late Monday to keep its power lines from igniting fires.

Hot, dry winds are forecast to blow across the region, threatening to knock tree limbs into power lines.

This is the first time PG&E has warned of shutoffs during this year's fire season.

Last year, when California's utilities first began carrying out widespread blackouts like this, some homes and businesses were left in the dark for days.

That drew outrage from state and local officials, triggered investigations and prompted PG&E to reassess the scope of future shutoffs.

The utility's weather models show that warm, offshore winds will develop Monday evening on the heels of the heat wave.

The soaring temperatures will further dry out grass, bushes and other vegetation, PG&E said.

Years of deadly fires started by PG&E's wires in wind storms forced California's largest utility to declare bankruptcy last year.

The company emerged in July after agreeing to pay US$25.5 billion (S$30.6 billion) to settle wildfire lawsuits.

The state has since set up a wildfire liabilities fund, essentially an insurance pool for the region's utilities, but just one catastrophic blaze could wipe it out.