The fire appears to have begun around noon at a home on Butts Canyon Road just north of the Aetna Springs Winery, said Scott Brown, a vineyard manager who lives a few hundred feet from the fire's origin.
Neighbors told him some young men accidentally started the blaze while cutting weeds using a tool with a metal blade, Brown said.
"I don't even let my guys mow the grass when it's like this," Brown said.
He was working about 8 miles away at a vineyard when he got word of the fire, and by the time he got home it had already raced across the hillside and destroyed some Quonset huts, he said.
In addition to being the driest year he can remember, it was 112 degrees in the shade on Monday, said Brown, who's lived in the Pope Valley for 45 years.
Berlant confirmed the person who reported the fire said it may have started with someone cutting weeds. He said investigators were looking into that possibility but had not confirmed that's how the fire began.
General contractor John Taylor lives off Snell Valley Road and received an evacuation order from Cal Fire.
"It's stressful, but that's what you get when you live out in the country," he said. He added he wasn't too scared by the blaze, saying he thought Cal Fire crews were doing an excellent job fighting it.
"Cal Fire is on it," he said around 7:30 p.m., moments before a spotter plane buzzed overhead guiding a large air tanker to the spot where it dropped a plume of red retardant near a house Taylor built in 2008.
"This has been a very fast-moving wildfire that has been driven by the terrain, hillsides, dry conditions and fanned by winds," Berlant said.