A firefighter walks near a backfire during the Saddleridge fire in Newhall, California. (AFP)

The wind-driven blaze sweeping through Los Angeles County's San Fernando Valley continued to spread Friday afternoon, destroying at least 25 homes and prompting mandatory evacuation orders for more than 100,000 people as California hits peak wildfire season.

At least one person is dead and one injured in connection with the fast-moving threat, which exploded from 1,600 acres just after 2 a.m. Friday to more than 4,600 acres less than two hours later. The disaster was fueled by the same dry, windy conditions that led a northern California power provider to shut off power to nearly 1 million people this week over fears of igniting another one of the massive fires that have plagued the state.

Officials warn that the Saddleridge Fire, now 13 percent contained, could keep growing as responders struggle to tamp it down amid heavy vegetation. Full containment could take days, they cautioned.

"It's not like your light grass fuels," said Los Angeles Fire Department Chief Deputy Dave Richardson. "It takes a lot more boots on the ground."

The brush fire started in the Sylmar neighborhood around 9 p.m. local time Thursday and was engulfing an estimated 800 acres per hour by the next morning. The cause of the fire is still unknown.

Authorities said Friday afternoon that flames remained most active at its northern edge. Activity in hard-hit Porter Ranch had calmed, but crews were still dealing with flare-ups, they said.

One man in his late 50s died overnight from cardiac arrest related to the fire, and a firefighter suffered an eye injury but is recovering, Los Angeles Fire Chief Ralph Terrazas confirmed Friday.

Authorities said swift cooperation with mandatory evacuations - still in place on 23,000 homes - helped keep the rest of the public safe. Los Angeles Police Commander Jeff Bert expressed his empathy for residents alarmed by door-knocks that came in the middle of the night with the news they had to leave. A year after California's deadliest wildfire on record, residents across the state are on edge.

"Being in a fire zone is terrifying," he said. "It's scary for me."

John Lee, a Los Angeles City Council member, warned people against returning to areas that no longer show smoke but remain under evacuation.

An aircraft helps fight the Saddleridge fire by dropping fire retardant along a ridge in Newhall. (AFP)

On Friday afternoon, the Red Cross said their five shelters in the Los Angeles area were quickly filling. North of Los Angeles at the Sylmar Recreation Center, 61-year old Sherry Glenn said she fled her Oak Ridge home with her son Jonathan, dog Paris, and a six-foot harp after receiving a mandatory evacuation notice by phone and then a visit by law enforcement. The fire had come to the hill next to their house as the sound of helicopters and "uncontrollably wild" winds swirled around them.

Glenn said this is her fifth evacuation since 2008.

"I love Sylmar. I love the San Fernando Valley," Glenn said. "But you know we get hit hard with winds and I've just learned to have all the pictures and things that are irreplaceable in a certain area."

All schools in the Valley were closed due to air quality concerns, while after-school activities were canceled, officials said.

Deputy Chief Al Poirier attributed the fire's speed to "extreme weather of high wind and low humidity" and warned the fire was moving westward. As of Friday morning, officials said Porter Ranch was the hardest-hit of the local areas.

"It'll likely end up in neighboring Ventura County before it's said and done," Deputy Chief David Richardson said during the news briefing.

"If we've learned anything, particularly from the Woolsey Fire, please heed the directions of your public safety officials: Evacuate. Do not wait to evacuate. Please leave when you have the opportunity to," Richardson said.

The Woolsey Fire ravaged nearly 100,000 acres north of Los Angeles in November, killing three people and destroying more than 1,600 homes and other buildings.

The Saddleridge fire's flames are being fanned by strong offshore breezes known as Santa Ana winds, which are notorious for raising wildfire risks in Southern California - particularly during the fall. Santa Ana winds transport extremely dry air toward the coast, with relative humidity hovering in the single digits in parts of Los Angeles on Friday.

This creates ideal conditions for rapidly spreading wildfires that can be nearly impossible to contain until the weather changes. The National Weather Service is warning that winds may not peak until midmorning Friday, with gusts up to 65 mph possible in some spots along the border between Los Angeles and Ventura Counties.

Red flag warnings for "extreme" to "critical" wildfire conditions have been extended through Saturday for parts of the two counties, as winds are expected to weaken but remain gusty overnight and into Saturday.

Despite the wind, fire officials said, air tankers were able to drop retardant in an effort to box in the blaze battled by a thousand firefighters. Water-dropping "Super Scooper" aircraft, helicopters and bulldozers were deployed too.

Some local residents documented their up close encounter with the fire. In one video, a woman lurches her car on a road toward a flaming orange oblivion. "I can't even see," she says as her daughter records the moment. "We gettin' the hell out of here."

Firefighters work as the Saddleridge Fire burns in Porter Ranch, California. (AFP)

Meanwhile, the fires paralyzed Los Angeles highways after official closed four major thoroughfares, including Interstate 5, the Los Angeles Times reported. Officials warned drivers to avoid all roads if possible.

The dryness and winds set the stage for the Sandalwood Fire, another fire in Calimesa to the east. It was triggered by burning trash dumped by a garbage truck caught on video flying down the street in a swirl of smoke.

Hundreds evacuated a mobile home park after the Sandalwood Fire swept through a dry grass field and into the community. Rosie Castellon, a resident there, was separated from her dog.

Monster was still in the home and first responders forbade Castellon from braving the flames to rescue her pet, she told the local NBC station. But her paramedic cousin arrived and made the rescue, she said.

The status of her home was less certain. "It's in the middle of that black smoke," she said, looking back toward the community. "I don't know if it's still standing."

By Friday afternoon, officials were looking ahead to plans for a recovery fund for affected residents and efforts to secure state and federal assistance. Grants authorized by FEMA mean that 75 percent of firefighting costs will be borne by the federal government, Congressman Brad Sherman, D-Sherman Oaks, said. It's still unclear whether a federal disaster declaration will provide additional help to businesses and homeowners, he added.

The Saddleridge Fire comes on the heels of California's most destructive wildfire season in history. In 2018, blazes raged in both the northern coast, more than 150 miles northwest of Sacramento, and in Los Angeles County to the south.

The Mendocino Complex fire to the north began in late July with the Ranch Fire that later converged with the separate River Fire. The collective blazes raged for more than three months and laid waste to 459,123 acres - roughly three times the size of Chicago.

As the Mendocino Complex Fire was contained, the Camp Fire broke out in Butte County north of Sacramento in early November. Though it burned less than a third of the acreage of the Mendocino Complex Fire, it became the state's deadliest fire on record, killing at least 86 people.

Around the same time, the Woolsey Fire engulfed a section of Southern California, torching 96,949 acres and forcing some 295,000 people from their homes.

Firefighters check on a backfire during the Saddleridge fire in Newhall, California. (AFP)

The 2018 wildfire season was especially ferocious due to record-breaking heat in the summer, which only exacerbates wildfire risks in the state's already dry, windy climate.

Anticipating high winds earlier this week, California energy giant Pacific Gas & Electric shut off power Wednesday night. The shutdown affected three-quarters of a million residents across 20 counties, mostly north of San Francisco; as of Friday, power hasn't been completely restored to all areas.

The energy company, whose equipment was deemed responsible for the November Camp Fire, made the unusual - and controversial - decision to enact the planned shutdown in an attempt to curb another round of disastrous fires, which are sometimes sparked when high winds bring down power lines in drought-stricken parts of the state.