A wildfire near Napa County's largest reservoir, Lake Berryessa, spread to 4,600 acres in about 24 hours, triggering evacuations as flames tore through a large swath of oak trees.
The Cold fire started about 4:30 p.m. Tuesday off Highway 120 west of Pleasants Valley Road and the picturesque city of Winters in rural Yolo County, swiftly scorching the dry grass and timber.
By Wednesday night, the fire was only 10% contained. Officials with the California Department of Forestry and Fire Protection said the volatile blaze was burning toward the north, often in remote areas that firefighters had difficulty reaching.
Late afternoon winds even sent flames over the fire line, forcing ground crews and aerial teams to rush to stem the break in the control boundary, according to Cal Fire. Low humidity and sweltering heat — temperatures in the 90s — also challenged the more than 620 firefighters deployed to the blaze.
The cause of the fire is under investigation.
Yolo County sheriff's deputies rushed to help evacuate dozens of residents at Golden Bear Estates and Canyon Creek Campground. So far, no homes have been destroyed, but flames threatened power lines along Highway 128, officials said.
Encroaching flames have prompted road closures on Highway 128 from the Monticello Dam to Pleasants Valley Road.
As the Yolo County fire burned, crews tried to gain control over the deadly Soberanes fire north of Big Sur on the Central Coast.
That destructive blaze, which started July 22 from an abandoned, illegal campfire, grew 2,400 acres to 46,700 due to dry conditions in Monterey County. The massive blaze is 27% contained and is still threatening 2,000 homes, prompting numerous evacuations.
Flames have consumed 57 homes, 11 outbuildings and five other structures. Bulldozer operator Robert Reagan III was killed July 26 while fighting the fire.
The more than 5,500 firefighters assigned to the fire have been hampered by the steep, rugged hillsides. Flames are burning in dense woodlands that are difficult to reach, officials said.
The blaze has triggered state park closures along the Central Coast through Saturday, as well as a host of road closures. Trails and roads within Los Padres National Forest's Monterey District were also closed.
Air quality officials were analyzing the impact of smoke on residents in the area.
In Fresno County, the Goose fire had grown to 2,241 acres and was 70% contained by late Wednesday, although much of the blaze was smoldering in remote areas, according to Cal Fire. Since it began Saturday, the Goose fire has destroyed four homes and threatened an additional 400 homes or structures.
Times staff writer Matt Hamilton contributed to this report.
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9:45 p.m.: This article was updated with additional details on the growth of the Soberanes, Cold and Goose fires.