At 2 a.m. most Napans are curled up in bed, but many wineries in the valley are waking up to the idea of having crews harvest grapes in the cool pre-dawn hours.

Vineyard managers say night harvests bring in grapes with better sugar levels, acid and “aromatics” — the scents that linger after the grapes go into the bottle.

Farmworkers work in cooler conditions, and dust is at a minimum.

Robert Sinskey Vineyards made the transition to night harvesting last year, according to vineyard manager Debby Zygielbaum.

Crews were out in Sinskey’s Carneros vineyards, just outside of Browns Valley, in the wee hours earlier this month.

“Picking at night is nicer and the crews don’t get as tired,” Zygielbaum said. “There is nothing worse than picking when it’s 100 degrees.”

Night harvesting does require extra equipment. Sinskey rents construction light towers fueled by diesel generators at the bottom of the light standards. Bright lights are also placed on the back of the tractors pulling trailers with plastic half-ton bins, into which crews dump the grapes.

Zygielbaum said fruit arrives at the winery before the heat of the day, between 6 to 7 a.m., and is immediately crushed and pressed.

Night picking doesn’t work in all terrain, Zygielbaum said.

Sinskey has one fairly steep terraced hillside vineyard, and vineyard managers are not certain it would be a good idea to give that a shot in the dark.

“You have to think about the possible dangers when being out there at night. You don’t want workers getting hurt,” she said.

During one recent night harvest, Sinskey’s two crews of six people each were able to pick for 11 hours “and that is unheard of if you are picking in the daytime. Even when the temperatures are in the 80s, that’s hot in the vineyard,” Zygielbaum said.

She said that so far there have been no complaints from neighbors. “I do try to make sure to call the neighbors to give them a head’s up that we will be picking.”

“We regularly call our neighbors to also let them know about sprays and such. I try to be as good a neighbor as possible,” Zygielbaum said.

Some vineyard managers have gone beyond stationary light towers that have to be periodically moved and instead decided to mount light towers on tractors and trailers.

At Napa Valley Reserve, ranch manager Mark Griffin said the Upvalley winery fabricated two sets of light towers. Griffin likes the fact that by picking at night the winery doesn’t have to give the fruit a cold soak.

In the Oak Knoll District, Trefethen Family Vineyards has been night picking since 2004, according to Jon Ruel, vice president of operations. Crews usually go to work at 2 a.m. and are home by noon.

Trefethen has perfected its own set-up of light booms, which can be tilted to light up four rows at a time.

“Once the workers get used to it, they prefer picking at night. Because they do such heavy physical work, the cooler temperatures allow them to work longer and pick more tons with the cooler temps,” Ruel said.

Ruel has made night harvesting a part of Trefethen Winery’s sustainability program. Picking at night translates into an energy savings for the winery because it does not have to cool the grapes before fermenting. Grapes picked during the day can reach 80 degrees.

“Now, Mother Nature does the cooling for us at night,” he added.

Ruel said he has received a lot of inquiries about night harvesting from other wineries.

He’s had vineyard managers come from Sonoma County and elsewhere to see night picking in action. “You are seeing more and more lights going at night these days,” Ruel said.