Thick smoke may hamper efforts to fight that fire in Henry Coe State Park from the air today.
Seven air tankers, including a DC-10, are available to pour water on the flames but a spokesman for Cal Fire says because of poor visibility aircraft will only be put in the air today as "the smoke allows."
The fire has now consumed nearly 19,000 acres.
It's 25 percent contained, but there's no word when firefighters will have the blaze encircled.
On the ground, firefighters battling the blaze continue to struggle against steep terrain and hot weather.
Temperatures are expected to be in the low 90s today.
The smoke from the fire has been spreading across the Bay Area, creating a brilliant red sunrise this morning but reducing air quality in the region.
Meanwhile, investigators have pinpointed the cause of the blaze.
Officials say it was sparked by an illegal debris burn that spread out of control.