There are five primary winegrowing zones within The San Francisco Bay AVA:
- Eastern Santa Clara Valley
- Santa Cruz Mountains adjacent
- Livermore Valley AVA
- Eastern Contra Costa
- Lamorinda AVA
Eastern Santa Clara Valley
Eastern Santa Clara Valley is the main, viticultural area within the Santa Clara Valley AVA. Most of the vineyards are located in the vicinity of Morgan Hill, San Martin, and Gilroy. The vineyards are on slopes and a range of alluvial soils, most of which drain well. There are some vineyards on flat lands with soils less optimal for high-quality wine.
The growing season temperatures are warm, increasingly so the further they are from the bay. As the AVA extends quite far south, all the way into San Benito County, Monterey Bay affects the climate in some areas. This is particularly true in Hecker Pass, just north of Gilroy.
Due to the warm climate and sunny, fog-free days, this area is good for robust red wine varieties, notably Cabernet Sauvignon, Zinfandel, and Syrah. In the cooler, Hecker Pass area, Pinot Noir and Chardonnay can do well.
Santa Cruz Mountain Adjacent
The Santa Cruz Mountains AVA was the first in the United States to be defined by a minimum altitude. The result is a region with complex, feathery edges, rather than boundaries that follow roads, streams, and other straight lines easily followed on a map. This means that the boundary lines cut through some individual properties. And, though the minimum altitude was meant to assure some consistency of temperature and sunny, fog-free hours between vineyards within the AVA, some out-of-the-AVA vineyards are quite similar too.
So, the Santa Cruz Mountain adjacent vineyards grow the same varieties as their neighboring vineyards within that AVA. And their weather patterns can be quite similar. For example, Portola Vineyards’ two acres of certified-organic Pinot Noir lie in the Santa Clara Valley AVA, but are literally across the street from the Santa Cruz Mountains AVA.
Livermore Valley AVA
The East Bay hills mostly protect Livermore Valley from bay influences such as fog and daytime temperature moderation. However, there is an important wind gap between the towns of Castro Valley and Hayward. High heat in the Inland Valley creates a massive low-pressure zone. Cold air rushes rapidly through the gap to equalize that pressure. Those winds can cool Livermore Valley by 40-50°F in just a few hours.
The very warm, sunny days followed by cool nights allow robust red varieties to ripen thoroughly, without losing too much acidity. Well-drained, gravelly soil contributes to that too. Varieties such as Cabernet Sauvignon, Petite Sirah, and Grenache thrive there.
Eastern Contra Costa County
The best-known growing area in eastern Contra Costa County is near Oakley with its sandy vineyards. Eastern Contra Costa is far removed from the main part of the bay by both distance and terrain; it’s twice as far from San Francisco as it is from Stockton.
The East Bay hills and Mt. Diablo lie between Eastern Contra Costa and the central portion of the bay. So, breezes reach the vineyards through San Pablo Bay, then the Carquinez Strait, and Suisun Bay, rather from the main part of the bay. The greater distance from the ocean and the more circuitous route for the wind mean less intense cooling for this area. Yet, although hot, the Eastern Contra Costa area’s temperatures are considerably more moderate than in the Inland Valley south of Stockton.
The warm weather and deep, sandy soils of the Oakley area are ideal for Zinfandel and Mourvèdre. Old vines of each continue to make excellent wines. (By the way, if you happen to see Small Berry Mourvèdre on a wine label using Oakley fruit, know that “Small Berry” is the name of the vineyard, not a description of the grapes.)
Lamorinda is a three-town area in the East Bay hills, east of the ridge that divides Alameda and Contra Costa Counties. The vineyards are small, with the AVA’s 139 planted acres (56 ha) split among 46 growers. Many, perhaps most, of the vineyards are in residential backyards. There’s not much opportunity for planted acres to grow significantly, since most of the total acres are either otherwise developed or too steep.
Modern winemaking in the area started with home winemakers fermenting their own small quantities of fruit. Almost all of the wine is sold very locally, as volumes aren’t high enough to support broader distribution.
The climate is warmer overall than in Livermore Valley to the southwest, because there is no wind gap funneling cold air and fog into Lamorinda. But, the AVA is not too far from the bay and is protected from the harsh afternoon sun by hills, so it is quite a bit cooler than the Oakley area.
The Lamorinda soils come from the hills themselves, Pliocene seafloor pushed up by tectonic movement. There is a mix of alluvial material, eroded from shale, sandstone, and clay stone.
Located in Contra Costa County on the east side of the Diablo Range (on the opposite side from Berkeley and Oakland) and stretching from those hills toward the Interstate 680 freeway.
The AVA is 29,369 total acres (11,885ha), 139 (56ha) of which were planted when the final petition was submitted in 2013.
The name is pieced together from the main towns that comprise the AVA: Lafayette, Moraga, and Orinda.
Topography/Elevation/Water Sources/Geographic Features
Moderate and steep slopes promote drainage, but make mechanized viticulture impossible
Thin, well-drained, clay-rich soils on top of uplifted, marine sedimentary sandstone and clay hardpan
Warm-summer Mediterranean. Days can be very hot, as the moderating effects of the Pacific are blocked by the hills. However, those same hills block the harsh, afternoon sun. Diurnal shift is less dramatic than in the Livermore Valley AVA, which experiences cold winds in the evening.
Main Grape Varieties
No dominant variety