A heat advisory for the area is in effect until 9 p.m. Saturday. Temperatures in Calistoga are expected to reach a low of around 59 degrees Friday night and a high of near 91 degrees on Saturday, with 5 to 7 mph winds. The chances of dry lightning are low but "not zero," the weather service said in its forecast discussion.

The area of the fire, which began shortly before 3 p.m. Thursday off Pickett Road east of Calistoga, increased to 4,690 acres overnight and containment remained at 7% as of 8:57 a.m., according to Cal Fire.

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

The Pickett Fire near Calistoga in Napa County expanded to 3,993 acres Friday night as firefighting efforts continued with night-flying helicopters and containment held at 7%, Cal Fire said.

In Napa County, the Pickett Fire has scorched over 1,000 acres in Calistoga, threatening several wineries and prompting evacuations