On a misty autumn morning in Sonoma County, Calif., Katie Jackson headed into the vineyards to assess the harvest. It was late in the season, and an army of field workers was rushing to pick the grapes before the first rains, however faint, began falling.

But on this day, Ms. Jackson, the vice president for sustainability and external affairs at Jackson Family Wines, was not just minding the usual haul of cabernet, chardonnay and merlot grapes. She also checked on the sophisticated network of systems she had put in place to help crops adapt to a changing climate.

Ms. Jackson, along with her siblings and mother, owns and operates Jackson Family Wines, one of the largest family-owned winemakers in the country. Best known for its Kendall-Jackson chardonnay, a supermarket staple, the family also produces dozens of other wines on five continents. After decades in the business, the Jacksons are sensitive to slight variations in the weather, and they are convinced of one thing: It is getting hotter and drier, and that could be a problem.

As California endures a yearslong drought, the Jacksons, like other winemakers, are grappling with new realities. Grapes, though a surprisingly resilient crop, are ripening earlier. Nights are warmer. Aquifers are running dry.