At 3 a.m. Thursday, Three Creek Vineyard in the Santa Ynez Valley was in full swing.

Lines of pickers were methodically moving down each vine picking cabernet sauvignon grapes by the light of spotlights mounted on tractors.

“When rain is imminent, a wrench gets thrown in everything,” said Erik Mallea of Coastal Vineyard Care, a vineyard management company that oversees Three Creek Vineyard and manages more than 2,000 acres.

“We were overcapacity and had two sleepless nights. We would pick from 6 p.m. to 2 a.m. and from 3 a.m. until noon.”

Many vineyards now harvest their grapes at night because it keeps the grapes cool, resulting in better wine, Mallea said. High daytime temperatures can change the sugar composition of grapes, while picking at night when sugar levels are stable allows for a more controlled winemaking process, according to Andrew Murray of Andrew Murray Vineyards.

“A pervasive trend is the care growers put in to get good fruit. Night harvesting is a big deal because they are picked when they are nice and cold and have maximum acidity,” meaning more reliable alcohol levels, Murray said.

“If you are picking them in the heat of the day, the vines are tired, the sugars are rising, acids are falling and it’s tough to cool down for pre-fermentation. It makes all the difference.”

Coastal Vineyard Care workers were pulling in about six tons of grapes a day ahead of Friday’s rains, which are expected to continue through Saturday. The forecast calls for an inch of rain and the possibility of gusty winds and small hail, according to the National Weather Service.

“Every storm increases the chances of rot,” Murray said. “The grapes will suck up the water, so that effectively delays ripening and lowers the alcohol content.”

Frosts in the spring and during the past two weeks coupled with dramatic climate swings decreased yields 20 percent to 40 percent, Murray said, adding that although that has a direct impact on profit, it can be a blessing in disguise.

“Crops were bigger last year,” he said. “This year, the diminished yields means the grapes can get ripe (quicker).”

Although Murray and Three Creek Vineyard have completed their harvests, there’s still fruit hanging in other vineyards.

“We’re pretty lucky,” said Prscilla Higgins, who owns Three Creek Vineyard with her husband, Roger. “I think our vineyard came out with one of the best yields, they ripened up. The problems stemmed from a late frost in April and May.”

Vineyard owners are hopeful that the mad dash paid off. Mallea said people are raving about the pinot noir and are excited about the quality so far this year.

“If we continue to make superior wines like we have in recent vintages, the popularity of these wine growers will increase,” he said, “and that’s important.”

— Noozhawk business writer Alex Kacik can be reached at akacik@noozhawk.com. Follow Noozhawk on Twitter: @noozhawk, @NoozhawkNews and @NoozhawkBiz. Connect with Noozhawk on Facebook.