On infrared satellite maps, the August Complex fire burning in some the most remote forests of Northern California shows up as an advancing serpentine, moving west in the mountains east of the Central Valley and along a front that now stretches almost 100 miles from north to south.

The largest wildland blaze in California history, the 877,477-acre fire complex stretches across five counties and has scorched areas rich with wildlife ― in the Mendocino National Forest, the Yolla Bolly-Middle Eel Wilderness, the Shasta-Trinity National Forest and Six Rivers National Forest.

The inferno’s official size jumped by about 300,000 acres late last week after officials folded in other large fires that had merged in the region.

And now its nearly unrestrained push west puts it on a path out of the wilderness and into the heart of California’s rugged and famed Emerald Triangle marijuana region at the most active and perilous time ― the run-up to the cannabis harvest.

“There are thousands of folks that migrate into Mendocino, Humboldt and Trinity counties every year, and they are not familiar with the territory let alone a massive wildland fire knocking at their door,” said state Sen. Mike McGuire, who represents the North Coast.

The region’s rural communities have been rooted in cannabis cultivation for decades. But the same sheltered landscape that gave rise to a black-market pot empire ― thick public and private forest ― is also likely to sustain flames until significant rains arrive, which could be weeks or months away.

That leaves the August Complex, at only 28% containment Sunday, on track to become California’s first million-acre wildland blaze, which would double the size of the largest-ever inferno, the 2018 Mendocino Complex in Lake and Mendocino counties.

The fire has already burned around the community of Kettenpom in southern Trinity County. It threatens to push toward Alder Point in Humboldt County and has burned into the ridges outside Covelo in northern Mendocino County.

Further south, flames on the western perimeter could threaten a critical communications tower on Mount Sanhedrin outside Potter Valley. Its southern edge could threaten the Lake Pillsbury Ranch, a rural Lake County subdivision.

Mendocino County Sheriff Matt Kendall said though the population of Covelo is typically about 1,500, at this time of year it can balloon to more than 10,000 people living and working on surrounding cannabis farms.

Kendall said he and other sheriff’s officials have taken part in radio broadcasts in the Covelo area, hoping to educate and prepare people, especially those unfamiliar with wildfire in California.

His greatest fear is that cannabis workers won’t evacuate in time if and when the fire comes.

“People should not be weighing economics with health and safety,” Kendall said. “We come into this world buck naked with nothing but the love of our parents. There’s nothing material on earth worth losing your life over.”

Kendall said Sunday that cooler weather and minimal winds have helped firefighters get equipment and personnel into hard-to-reach terrain to start building fire breaks and protect forested communities on the massive fire’s outskirts before drier and potentially windier days ahead.

“You can have all the equipment in the world, but when you have roughly of 120 miles of fire line engulfing the entire eastern line of Mendocino….” Kendall said, trailing off as he tried to describe the scale of the fire.

“The chess board is being set,” Kendall said. ”But if that wind picks up, everyone in those areas should be extremely concerned.“

What is now the August Complex started as about three dozen separate fires scattered throughout the Mendocino National Forest and further north. The fires ignited Aug. 16 and 17 during a dry lightning storm, a meteorological phenomena that hit Northern California at a time of severe drought and changing climate conditions that left forests susceptible to burn.

A lightning strike during the same storm is presumed to have also started the 55,209-acre Walbridge fire north of Guerneville and west of Healdsburg in Sonoma County.

Both blazes are what fire bosses call “a dirty fire,” with flames that leave islands of unburnt ground in larger swaths of scorched earth ― in this case, forests.

“It didn’t burn clean. There are islands in there and every now and then an island will burn,” Monte Rio Fire Chief Steve Baxman said of the Walbridge fire. “This fire will not be out until we get 6-to-8 inches of rain.”

Sunday, the Walbridge fire was 96% contained, a scant gain reflective of the work still needed to control the fire in steep terrain near Red Slide northwest of Austin Creek State Recreation Area.

A special fuels crew from the Geyserville Fire Protection District was working with Cal Fire to dig containment lines by hand, Baxman said.

“Every now and then there will be stump or a piece of the tree that will flare up,” Baxman said. “They are working the edges, working a quarter mile in where they can. This will be a project.”

Across California, 3.3 million acres have burned so far this year, including 29 major fires currently ablaze. Twenty two people have been killed in the state and over 4,100 structures destroyed.

One of those fatalities included a volunteer firefighter from Texas working on the August Complex in the Mendocino National Forest.

Lake County Sheriff Brian Martin said that he was keeping close track of the fire’s southern edge near Lake Pillsbury Ranch, a community near the Eel River reservoir with many vacation homes and roughly 30 fulltime households.

“We talked with some people who chose to ride it out,” Martin said. “They thought they were better off defending their property. We of course encouraged them to go.”

McGuire traveled on Sunday through remote areas threatened by the August Complex. He recalled a moment in Kettenpom, with a little more than a general store and gas station serving hundreds of residents, mostly cannabis growers, who live in the surrounding hills.

“It’s surreal to be standing at the Kettenpom fire department in Trinity County and see three fire engines and a fire pickup from New Jersey drive by, heading into the fire,“ McGuire said.

You can reach Staff Writer Julie Johnson at 707-521-5220 or julie.johnson@pressdemocrat.com. On Twitter @jjpressdem.