Record heatwave threatens California's power grid

Record heat has scorched parts of California, as power operators urged residents to cut back usage in the late afternoon to avoid rolling blackouts caused by high demand for air conditioning.

Among the highest temperatures expected on Tuesday was a record-setting 46C in the state capital of Sacramento, the National Weather Service said.

The heatwave, which began in Southern California last week and moved north over the Labor Day weekend, brought all-time high temperatures for September 5 to San Francisco, Oakland, San Jose and other nearby cities, the National Weather Service said.

The hottest day of the heatwave was expected to be Tuesday, and California Governor Gavin Newsom said the risk of power outages was real and immediate.

"This heatwave is on track to be both the hottest and longest on record in the state and many parts of the West for the month of September," Newsom said in a video sent to reporters.

The weather has also made it more difficult to fight wildfires, as hot air dries vegetation that can fuel blazes.

READ MORE: California blaze destroys 100 homes as thousands flee

Residents told to conserve power

On Monday, a rapidly expanding wildfire in Riverside County, east of Los Angeles, killed two people and injured a third. On Tuesday, it was only 5 percent contained, according to the California Department of Forestry and Fire Protection (Cal Fire).

Over the past week, a fire in the far northern portion of the state killed two people and destroyed hundreds of homes and buildings in and around the city of Weed. As of Tuesday morning, that fire was 55 percent contained after scorching some 4,300 acres.

In Livermore, east of San Francisco, temperatures hit 46.6 C on Monday, blasting through the previous high of 42.2 C in 1950.

The California Independent System Operator, which manages much of the state's electrical grid, extended its call for residents to set thermostats to 25.5 C and avoid using large appliances during the hours of 4 pm to 9 pm. 

During those peak hours, power generated by solar and hydroelectric resources begins to fade yet demand for air conditioning remains high as inland areas hit the hottest parts of their day.

Other power managers, including the Sacramento Municipal Utility District, asked residents of the hard-hit state capital region to conserve even more, setting their thermostats to 80 degrees to help avoid blackouts.

The heat, which is expected to continue through Friday, is leading to record demand on the energy grid, said Newsom, whose office has asked residents to chill their homes in the cooler mornings to 70 degrees, and then set thermostats higher in the afternoon and evening.

More than two decades of drought and rising temperatures, exacerbated by the climate crisis, have made California more vulnerable than ever to wildfires. The two most devastating years on record were in 2020 and 2021, based on the number of acres burned.

READ MORE: Thousands flee as California blaze injures residents, destroys homes