Firefighters battling the Pickett Fire in California Wine Country are holding the line on acreage and continuing to increase containment with the help of favorable weather conditions, Cal Fire reported.

The fire in Napa County near Calistoga has been burning since Aug. 21, threatening a number of vineyards and wineries within the evacuation zones. While the footprint of the fire has remained stable, smoke from the fire could impact the area's grape harvest.

The overnight marine layer of low clouds and fog moving in from the Pacific Ocean — in which cooler, moist air is trapped near the surface by the warmer, drier air above it — is helping crews in lower elevations, Cal Fire said in a Wednesday status report on the fire.

Cal Fire said the fire's containment crept up to 29%, while the size remained at 6,803 acres, about twice the size of the city of St. Helena. The fire was expected to remain in its current footprint, the agency said, which is near several vineyards.   

Firefighters were strengthening control lines and mopping up hot spots, while damage assessment teams were working to identify structures in the fire's path, Cal Fire said. There were at least 292 structures that were threatened by the fire, but no structures were destroyed.

Nearly 3,000 fire personnel were working the Pickett Fire as of Wednesday afternoon. Among the resources assigned were 11 helicopters, 251 engines, 62 dozers, 35 water tenders, and 61 hand crews.

Current Pickett Fire evacuation areas 8/26

Evacuation orders remained in effect for the following zones as of Wednesday afternoon. Residents can find their evacuation zones at protect.genasys.com.  

• NPA-E107-B
• NPA-E108-A
• NPA-E114
• NPA-E115
• NPA-E122-B
• POP-E001-B
• POP-E002-C

Meanwhile, evacuation warnings were in effect for these zones:

• NPA-E120
• NPA-E121-B
• NPA-E121-C

The Pickett Fire started just before 3 p.m. on August 21 in the area of Pickett Road northeast of Kenefick Ranch Vineyard and Winery, outside Calistoga city limits.

No injuries have been reported, and the cause of the fire is under investigation.