▶ Watch Video: Western states battle wildfires, record heat and power shortages

Los Angeles — Much of the western United States was still baking on Monday morning as a blistering heat wave continued, fueling wildfires that were forcing evacuations in northern California. Some 30 million people were under excessive heat warnings and advisories on Monday, with multiple cities hitting record-high triple-digit temperatures and the fires turning deadly.

Federal investigators were looking into the crash of a fire survey plane in Arizona, which left retired fire chief Jeff Piechura and his pilot dead.

CBS News lead national correspondent David Begnaud reported from Los Angeles that officials were keeping a very close eye on how the blazes could impact California’s power grid. Fires in Oregon knocked-out three major power transmission lines to California.

Combined, the downed lines supply about 10% of California’s energy, or around 5,500 megawatts — the amount it takes to power every home in Los Angeles County for two hours.

Early Monday morning, back-up systems were making up the difference, but the strain on the grid as the fires kept burning prompted officials to issue an urgent plea for Californians to conserve energy.

In Northern California, the so-called Beckwourth Complex Fire turned at least 20 homes to ash and roads into raging infernos as it grew into the largest wildfire the state has seen yet this year, covering an area almost triple the size of San Francisco.

Area resident Phil Burgarello said that, at first, he tried to keep the fire at bay as it approached his house, wielding only a shovel and some water, but he was soon overpowered. 

“The flames are big, and they’re hot,” Burgarello said after losing the fight, and his home.  

A firefighter sprays water while trying to stop the Sugar Fire, part of the Beckwourth Complex Fire, from spreading to neighboring homes in Doyle, Calif., Saturday, July 10, 2021. 

Noah Berger / AP

In Oregon, just north of the California border, the Bootleg Fire exploded over the weekend.

“We are seeing doubling in size of the fire every 24 hours,” Oregon State Fire Marshal Gert Zoutendijk said on Saturday. “Basically every ember that falls will start a new fire.”

There was so much smoke and ash that it interfered with the power lines crossing the border into California, squeezing energy supplies to that state. Officials said they likely wouldn’t be able to restore the lines until Tuesday, at the earliest.

The extreme heat has driven the wildfires, but even as nearby Death Valley hit a sweltering 130 degrees on Friday — just four degrees short of the world record — tourists still braved the heat to visit California’s Joshua Tree National Park over the weekend.

“It feels like we’re in an oven,” said one park visitor.

With the three power transmission lines still down on Monday, energy officials issued what they call a “flex alert,” meaning there’s an urgent need for all Californians to conserve energy. The specific plea is for state residents to avoid using major, electricity-hungry appliances like ovens and dryers during the peak hours between 4 p.m. and 9 p.m. local time.