RUTHERFORD, Calif. — Driving north through the Napa Valley before sunrise, portable lights like spaceships illuminate workers in the vineyards. The smell of fermentation and grapes fill the air — the annual wine harvest is underway.

At Quintessa winery, grape picking began under a crescent moon at 4 a.m. Wednesday, with the fruit sorted and dropped into tanks a few hours later for fermentation. Napa is known for its Cabernet and brings in most of its grapes for red wines in early September. White grapes are harvested a month or two earlier.

Winemaker Rebekah Wineburg said Quintessa’s harvest began Sept. 8 and will continue through the end of October.

“There is an even pace of the harvest this year. The quality is excellent, and our yields are back to average, which is nice after the light yield in 2015,” Wineburg said.

Crews spread out over the Dragon’s Terrace vineyard, one of the winery’s premier vineyards, to pick Cabernet Sauvignon grapes amid the hum of tractors and workers yelling as they dropped grapes into bins.

Twenty tons of grapes were brought to the crush pad, where the fruit is sorted and de-stemmed before falling into the “gravity-flow winery,” where fermentation takes place.

Andy Beckstoffer of Beckstoffer Vineyards, who is one of the largest wine growers the valley, said this season’s batch should have enhanced flavors and less alcohol content.

“Harvest started at a normal time, but the cooler days at the beginning allowed for greater flavor development without much sugar accumulation,” he said.

Wineburg said she’s excited by what she is seeing with the harvest.

“It makes me expect another great vintage,” she said.