Carneros is the coolest of all AVAs nested within the Napa Valley AVA. In my opinion, it is also the most versatile of them. It produces crisp sparkling wines but also excellent Merlot and Syrah. 

The Carneros AVA actually straddles the Napa-Sonoma County line though. It even represents more acreage in Sonoma County than in Napa County. But, Sonoma County has so much vineyard acreage in close proximity to the Pacific Ocean, Carneros’ cool-to-moderate climate is less unique to Sonoma County than it is to Napa County.

Mediterranean Climates

Like many of California’s wine-growing regions, including all of Napa, Sonoma, and Mendocino counties, the Carneros AVA has a Mediterranean climate. The hallmarks of such climates, which are heavily moderated by large bodies of water, include long, sunny growing seasons with little rain, mild weather during spring and fall, and winters that are cool to cold, but not frigid. Most rain falls during winter.

Oceans, seas, bays and large lakes act like a heat sink. They essentially absorb heat on warm days and release it on cold ones. Winds flowing from the water communicate that cooling or warming well inland, unless thoroughly blocked by high mountain ranges.

The Pacific Ocean is quite cold, compared to the Mediterranean Sea, so it generates fog. That fog slows grape ripening by providing further cooling at night, inhibiting temperature rise in the morning, and also blocking morning sunlight.

Low clouds coming off San Pablo Bay can filter sunlight, lower temperatures, and make dramatic photos.

Carneros’ Climate

The Pacific is the primary moderating influence on most of California’s Mediterranean climate regions. But, while the ocean is a factor for Carneros, San Pablo Bay is a more direct influence. On the Napa side, Carneros’ southern border is very close to the broad Napa River wetlands which lead into that bay, and just four miles from San Pablo Bay itself. The southernmost portion Sonoma-side Carneros is even closer to the bay, roughly a mile. Afternoon breezes coming off the bay are cool and often quite strong. Daytime temperatures rarely break 80 degrees.

Carneros doesn’t get much rain, about 18 – 27 inches in typical, non-drought years. That’s less rain than any other AVA in Napa. Only four or five of those inches come during the growing season, mostly during spring. 

Since there is minimal risk of significant, late-season rain and, because of the cool temperatures, little risk of excess sugar accumulation, the growing season can run late into the year. With the slow, even ripening, color, tannins, and fruit flavors can be well-developed while plenty of acidity remains. 

Soils

Carneros AVA soils are primarily clay. 10,000 to 15,000 years ago, San Pablo Bay stretched much farther north than it does today. Carneros was under water. So the topsoils are derived from material carried downstream by the Napa River, erosion from hills, and accumulations from the bay. There is variation in soil from place to place within the AVA, but the predominant soil is called Haire-Coombs.

Beneath the topsoil, the clay has been compressed into a thick, impenetrable hard pan. Think of it as concrete. Vine roots can’t usually force their way through it. On slopes, the rainwater drains through the shallow topsoil and then runs downhill.

Sloping and hilltop vineyards in Carneros typically require irrigation, since there’s not enough water-holding capacity in the soil to conserve moisture from the winter and spring downpours. In the level areas south of Carneros, the water table is too high for wine-growing. It’s better for sheep and cattle grazing, field crops, and water fowl. Close to the bay, the water table is also too saline for vines.

While irrigation is necessary during summer, the clay soils do hold water into spring. This has a cooling effect on the vines and tends to delay bud break. During the heart of the growing season, the dry, shallow topsoils limit vigor.

Los Carneros Name

The name dates back to one of the original Spanish land grants in the area. There was a creek named Carneros and also parcel called “Rincon de los Carneros” or “corner of the rams.” It’s not clear to me which took its name from the other.

The original, official name for the AVA was Los Carneros. Now, Carneros is also legally acceptable. Either name can appear on wine labels. There’s no meaningful difference between the two and producers use whichever one they prefer.

Both the Napa Valley AVA and Sonoma County have conjunctive labeling laws. They dictate that a wine label which bears the name of an AVA nested within them must also list the name of the larger geography. In other words, a Rutherford District wine must also have Napa Valley on the label. However, because this AVA falls into both regions, the conjunctive labeling laws don’t apply to Carneros. Yet, for wines made with fruit predominantly from one side or the other, wineries sometimes choose to make that clear by listing either Napa Valley or Sonoma County too.

Carneros History

It’s certain, based on documents from the time, that there was at least one vineyard and winery in Los Carneros as of 1872. By the end of that decade, there were more than 20 wineries and 357 acres of vines, about 10% of Napa Valley’s total vineyard land back then. Judge John Stanly established a vineyard there in the 1880s, a period when California vineyard acreage expanded rapidly. By the middle of the decade, Stanly alone had at least 200 acres under vine and a 100,000+ gallon capacity winery. 

Then phylloxera devastated vines in California, as it had in Europe. Prohibition wasn’t far behind. ln 1930’s, after Repeal, the only wineries there were Stanly and a new one called Garretto. It wasn’t until about 1964 that significant new plantings were established there, first by Beaulieu Vineyards and Louis Martini, then Robert Mondavi Winery, Charles Krug and Domaine Chandon. Stanly Ranch, still an important Carneros vineyard, now belongs to Starmont Winery.

Wine Styles

As with much of both Napa and Sonoma Counties, the climate in Carneros is very good for viticulture. Wineries can make wines in the style of their choosing, rather than being limited by climate-related concerns. Due to the relatively cool climate and potentially long growing season, grapes in Carneros can achieve excellent color, soft tannins, and well-developed flavors, yet make balanced, juicy wines which don’t taste of baked or dried fruit. 

At the time the AVA was established, proposers said there was a recognizable typicality to the red wines of Carneros. However, even the best of those people, including Robert Mondavi, Louis Martini, and Brother Timothy of Christian Brothers were at a loss to define it specifically. They spoke generally to the color and texture, essentially suggesting that you know it when you see or taste it. 

However, that was nearly 40 years ago. Today, there are many more vineyards and they cover much more of the AVA, whereas most of the vineyards had only been in the hills and some narrow valleys. That, broadening tastes in wine, and, perhaps, a touch of climate change, lead to much more diversity among the wines now. Both Pinot Noir and Chardonnay wines range from medium body to full and from medium alcohol to high.

See my articles on specific wines and wineries of Carneros.

Carneros AVA Details

Established: 1983

Latitude: degrees

Elevation: 0-700 feet, avg. 123 feet

Climate: Mediterranean

Average Growing Degree Days: 2996*

Biologically Effective Degree Days: 1755*

Winkler Classification Region: upper end of Region Ib

Annual Rainfall: 18-30 inches

Soils: Clay dominated. Some areas feature hard pan subsoil, which inhibits deep rooting.

Total Acres: 37,213

Vineyard Acres: roughly 9,000

Wineries: 

Primary Red Grape Varieties: Pinot Noir, Merlot

Primary White Grape Varieties: Chardonnay

*average of data provided by vineyards to everyvine.com.

Copyright Fred Swan 2018. Images courtesy of Carneros Wine Alliance. All rights reserved.