While much of California’s Sonoma County is warm all year round, the maritime climate of its coastal wine-growing regions is a viticultural sweet spot, combining cool, even temperatures, cold winds and fog. A Pacific marine layer cools down those appellations closest to the coast each morning, lingering in some places before burning off in the midday sun. Cold ocean air funnels its way inland from the coast through corridors, resulting in high winds that affect grape-growing conditions.
The AVAs (American Viticultural Areas) acknowledged as the most heavily influenced by coastal conditions are West Sonoma Coast, Petaluma Gap and – moving inland a little – the Green Valley of Russian River Valley. While they are by no means the only regions in Sonoma County where cool-weather vineyard sites can be found, they are the AVAs that focus almost exclusively on the cool-climate, Burgundian varieties of Chardonnay and Pinot Noir.
BEYOND TEMPERATURES Other than a cool climate, there are other factors that impact grape ripening in Sonoma County. The first thing to note is that ‘cool’ does not just mean temperature. While it certainly plays a starring role, you can’t base ripeness solely on heat or degree-day accumulation. Geological and topographical factors, as well as slope aspect, can significantly impact ripeness, while elements such as sunlight and wind are essential to the fruit’s maturation. ‘Wind, in particular, has a few noteworthy effects,’ says Brian Maloney
