SANTA CRUZ, Calif. — A series of wildfires burning an area larger than the state of Rhode Island has depleted California's firefighting resources and triggered requests for help from across the West, the East Coast and even as far as Australia.


Since Saturday, more than 771,000 acres of California's forests and shrub lands have burned, many of them sparked by a weekend lightning storm stretching hundreds of miles and stoked by one of the worst heat waves in recent memory.


"These fires again are stretching our resources, our personnel," Gov. Gavin Newsom said during a Friday media briefing.


More than 12,000 firefighters aided by helicopters and air tankers are battling wildfires throughout California. Three groups of fires, called complexes, burning north, east and south of San Francisco have together scorched 991 square miles (2,566 square kilometers), destroyed more than 500 structures and killed five people.


At least 100,000 people are under evacuation orders.


About 96% of the fire engines with the California Department of Forestry and Fire Protection, or Cal Fire, are already committed to wildfires, with little in the way of local assistance. Oregon, Arizona and Washington have all sent firefighters and equipment to help, and there's a pending request with Australia for that country's fire crews, Newsom said.


The blazes, coming during a heat wave that has seen temperatures top 100 degrees, are taxing the state’s firefighting capacity but assistance from throughout the country was beginning to arrive, with 10 states sending fire crews, engines and aircraft to help, Gov. Newsom said.


But not all requests from California for out-of-state resources are being granted. Officials with the National Interagency Fire Center in Idaho, which coordinates interstate firefighting deployments, said they've been inundated with requests from across the West and have redirected some of California's requests back home.


"It's difficult with what's happening across Northern California right now," said Sean Kavanaugh, Cal Fire's incident commander on the LNU Lightning Complex fire, which is burning in Napa, Sonoma, Lake, Yolo and Solano counties.


Tens of thousands of homes were threatened by flames that drove through dense and bone-dry trees and brush. Some fires doubled in size within 24 hours, fire officials said.


With firefighting resources tight, homes in remote, hard-to-get-to places burned unattended. CalFire Chief Mark Brunton pleaded with residents to quit battling fires on their own, saying that just causes more problems for the professionals.


"We had last night three separate rescues that pulled our vital, very few resources away," he said.


While the fires could not be predicted, the strain on firefighting resources was.


Cal Fire's union leadership began sounding the alarm about a depletion of resources in the spring, when the COVID outbreak triggered early releases from prisons and with that, a loss of hundreds of inmate firefighters who annually help set up defensive lines around wildfires. Inmate firefighters make up about 43% of Cal Fire's firefighting force.


Since the outbreak began, the California Department of Corrections and Rehabilitation has released more than 800 inmate firefighters, with about 600 of those releases coming since July.


"A combination of expedited and natural releases have contributed to the recent decrease in the conservation camp population," CDCR spokesman Aaron Francis said in an email.


The state is down to 1,659 inmate firefighters from the 2,255 available in April.


Overall, 1,300 inmates are deployed across the state assisting with some of the most grueling work in firefighting: marching into rugged terrain with hand tools to cut away brush and scrape the earth free of anything that could burn.


The state hired some 800 seasonal workers "just in time" to offset the loss in inmates at the cost of about $72 million, Newsom said.


"We have more people, but it's just not enough. We have more air support, and it's still not enough," the governor said.


The fires in Northern and Central California have killed at least five people, destroyed more than 570 structures and scorched over 1,200 square miles, more than twice the area of the city of Los Angeles. A Pacific Gas & Electric worker also died at the time of the fires, but Cal Fire officials say it was unrelated to the blaze.


"We can confirm that a Vacaville-based troubleman passed away while assisting first responders as they dealt with the LNU Complex Fire," PG&E said in a statement. "Out of respect for the family's privacy, we won't be sharing additional details at this time."


More than 60,000 people were under evacuation orders Friday in Santa Cruz and San Mateo counties, as firefighters hoped to use a break in the extreme heat to make progress against the raging fires.


Cal Fire’s Brunton said the area was still burning Friday. Some cooler, moist air did arrive Thursday evening, which slowed the fire significantly.


In fact, "once that marine layer pulled out, there was free burning activity out there again, which challenged all our lines out there, and burned in several different directions," said Billy See, one of the Cal Fire incident commanders.


See said nearly 100 more firefighters showed over the last day, bringing their force to about 1,000 people.


"It's still not enough," he said. "We're going to continue to bring additional personnel and resources in here."


Resources are coming in from other states, but it takes a matter of days for that manpower to arrive.


See has said this fire is historic. "I'm tired of saying that I've never seen something like this in 34 years of fighting fire," he said. "It's a dangerous situation."


The fire continued to burn through the mountainous Santa Cruz County communities of Boulder Creek and Ben Lomond, destroying a number of structures overnight.


"We can't save everything," Brunton said. "We have to pick and choose our targets of opportunity the best we can." Properties that have a cleared layer of defensible space _ no flammable vegetation in a zone around property _ give firefighters the best opportunity to save a home, he said.


The intense smoke caused by the fire, which is burning through timber, has limited the use of firefighting aircraft.


The evacuation zone for the fire stretches in the mountains from San Gregorio State Beach, south of Half Moon Bay, to the edge of the city limits of Santa Cruz. The orders reached the University of California, Santa Cruz campus late Thursday.


Then there were the blackouts, as the electrical grid was overwhelmed amid the heat.


With more than 18,000 students enrolled at UC Santa Cruz, the university is working to find hotel or other rooms for students, although it's unclear how many were on campus or in the community when the evacuations were announced.


The fire also seriously damaged Big Basin Redwoods State Park, northeast of Santa Cruz, prompting a conservation group Thursday to openly mourn the loss of California's oldest state park.


One major cluster of blazes is in wine country. The LNU Lightning Complex fire has blackened a combined 219,067 acres, destroyed 480 structures and triggered the evacuation of nonessential personnel from Travis Air Force Base in Solano County and patients from Adventist Health St. Helena hospital in Napa County. It was 7% contained Friday morning as the area cooled overnight. Travis Air Force Base in Fairfield canceled its evacuation order for nonessential personnel Friday morning.


Looking ahead, there is a chance that another string of lightning storms could hit the coastal mountains over the weekend, San Jose State atmospheric scientist Alison Bridger said.