Steady winds with gusts up to 45 mph with nearly non- existent humidity are expected to descend on the areas north of San Francisco where at least 23 people have died and at least 3,500 homes and businesses have been destroyed.
"It's going to continue to get worse before it gets better," state fire Chief Ken Pimlott said Wednesday.
Entire cities had evacuated in anticipation of the next wave, their streets empty, the only motion coming from ashes falling like snowflakes.
Tens of thousands more were also driven from their homes by the flames. A few left behind cookies for firefighters and signs that read, "Please save our home!"
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The 22 fires spanned more than 265 square miles (686 square kilometers) as they entered their fourth day, many of them completely out of control.
Modern, strategic attacks that have kept destruction and death tolls low in recent years just haven't worked against their ferocity.
"We are literally looking at explosive vegetation," Pimlott said. "Make no mistake," he later added, "this is a serious, critical, catastrophic event."
"That's very bad," resident Nick Hinman said when a deputy sheriff warned him that the driving winds could shift the wildfires toward the town of Sonoma proper, where 11,000 people live. "It'll go up like a candle."
The ash rained down on the Sonoma Valley, covering windshields, as winds began picking up toward the potentially disastrous forecast speed of 30 mph (48 kph).
Countless emergency vehicles sped toward the flames, sirens blaring, as evacuees sped away. Residents manhandled canvas bags into cars jammed with possessions or filled their gas tanks.
"We have had big fires in the past. This is one of the biggest, most serious, and it's not over," Gov. Jerry Brown said at a news conference Wednesday, alongside the state's top emergency officials.
They said 8,000 firefighters and other personnel were battling the blazes and more resources were pouring in from Arizona, Nevada, Washington and Oregon.
Flames raced across the wine-growing region and the scenic coastal area of Mendocino farther north, leveling whole neighborhoods and leaving only brick chimneys and charred appliances to mark where homes once stood.