The Petaluma Gap is part of the Sonoma Coast AVA, a designated American Viticultural Area, but is not yet an AVA. The Sonoma County wine industry adopted the term “Petaluma Gap” to help define its products, since the wind, fog and soils in the Gap give the area’s wine a distinctive character.
Geographically, the Petaluma Gap borders West Marin and Valley Ford on the west, then follows Chileno Valley and Spring Hill Roads to Adobe Road on the east, Cotati on the north and Lakeville on the southeast. This is not your normal geography. As inland valley air heats up, it pulls the cool coastal air into a naturally formed 15-mile-wide “gap” in the coastal range mountains. The wind flows off the ocean between Tomales Bay and Bodega Bay, builds up speed as it funnels through the gap, then empties into San Francisco Bay. Wind and fog define the area, giving the term “micro-climate” real meaning.
The daily weather pattern goes something like this: Early-to-mid-morning finds a distinctive crisp coolness and a blanket of fog. By late morning the sun has chased away the fog and the temperatures rise. By mid-afternoon, however, the cool breezes return, flowing west to east, picking up speed as the afternoon progresses and bringing in the almost nightly fog. There are daily temperature swings of forty to fifty degrees. This cooling “wind tunnel” effect means the vineyard yields are smaller and grapes ripen later, developing wonderful flavors and fruit characteristics, while maintaining ideal levels of acidity. It’s the perfect recipe for intense but well-balanced wines.