From USA Today:
At 4 o'clock in the morning, Shafer Vineyards is alive with light and motion. The sun won't be up for more than three hours, but lines of pickers are moving methodically down vines full of ripe cabernet sauvignon grapes. They're lit by huge bright lights mounted on tractors trundling alongside.
The scene at this vineyard is part of a worldwide practice that's increasingly the way all wine grapes are harvested — in the dead of night. It results in better wine, lower energy costs and happier workers.
Daytime temperatures in the 90s and above change the sugar composition of grapes. Picking at night when sugar levels are stable keeps "surprises" from happening during fermentation such as wild yeast starting fermentation, says Shafer's Andy Demsky.
Pickers can work longer hours in the lower temperatures and also avoid the "wasps, bees and rattlesnakes" that come out during the day, he says. And the grapes are picked cool, saving energy because they don't have to be pre-chilled before they're crushed.
For more, see: California vineyards find night harvests yield benefits