Wildfires have cropped up in different regions across California over the past several days as a record-breaking heat wave blankets most of the state, with more fire activity expected amid a spate of dry lightning and thunderstorms.

According to Cal Fire, the blaze had reached 4,690 acres as of Saturday, and was 7% contained, with crews working overnight to keep the fire within control lines.

The Pickett Fire was reported shortly before 3:30 p.m. Thursday. The California Highway Patrol initially reported smoke was visible from Highway 128.

The Pickett Fire near Calistoga nearly doubled in size Thursday night, reaching 2,131 acres with no containment, according to Cal Fire.

Firefighters will battle intense heat and dry weather Friday as they work to control a fast-moving blaze in the heart of California’s wine country.