Napa Valley Wine Region

Posted August 1, 2010; updated October 3, 2015

  • Appellation​ - Napa Valley
  • Sub-appellation(s)​ - Atlas Peak, Calistoga, Chiles Valley, Diamond Mountain District, Howell Mountain, Los Carneros, Mt. Veeder, Oak Knoll District, Oakville, Rutherford, Spring Mountain District, St. Helena, Stags Leap District, Wild Horse Valley, Yountville.
  • Location​ - United States (Napa County, California); 38th parallel.
  • Size​ - 485,102 acre (45,275 acres planted to vineyards)
  • Rainfall​ - 23.7 in/yr (600 mm/yr)
  • Growing Degree Days​ - 2,300-3,300 (depending on specific area)
  • Grape Varieties​ - Cabernet Franc, Cabernet Sauvignon, Chardonnay, Dolcetto, Malbec, Marsanne, Merlot, Pinot Gris, Pinot Noir, Petit Sirah, Petit Verdot, Rousanne, Sangiovese, Sauvignon Blanc, Syrah, Tempranillo, Viognier, Zinfandel
  • Claim to Fame​ - Most renowned New World wine region; classic Cabernet Sauvignon & Chardonnay; Paris Wine Tasting of 1976. 

View Other California Wine Regions

Previous California Vintage Notes

  • 2009 - Edna Valley
  • 2010 - Napa Valley
  • 2012 - Edna Valley

Napa Valley is considered one of the world's finest wine growing regions. Its first wine grapes were planted in 1838 by George C. Yount and commercial winemaking followed just twenty years later. As the region's acclaim grew, the industry exploded. By the turn of the 19th century, there were over 140 wineries operating in Napa Valley, including Charles Krug, Inglenook, Schramsberg, Beaulieu, and Beringer (shown left).

Phylloxera ripped through Napa Valley in the early 1900's. These tiny insects destroyed over two-thirds of European vineyards in the late 19th century, but decimated nearly 80% of Napa's vineyard plantings. An even bigger hit to the region's wine industry was Prohibition, which effectively shut down wine production for 14 years. Once Prohibition was repealed, production quickly met and exceeded previous volumes. This era also saw the introduction of modern winemaking practices by Russian immigrant Andre Tchelistceff, largely credited with making California's wine industry what it is today. Napa's defining moment on the international stage came in the Paris Wine Tasting of 1976, when Napa Cabernet Sauvignon and Chardonnay bested many of France's most revered labels. 

Today, Napa Valley is home to over 450 wineries and 45,000 acres of vineyards. Surprisingly, it only accounts for 4% of California's total wine volume. Driving through the valley on Highway 29, one quickly sees how much time, effort, and money has been invested in the breathtaking estates flanking the streets.

Napa Valley snakes thirty miles northwest from the San Pablo Basin, bounded by the Mayacamas Mountain Range on the west and the Vaca Mountains on the east. Following the Napa River north, the valley tapers from about five miles in width at its base to just one mile at the top. The diversity of topography, soils, and climatic conditions have led to the valley's segregation into fifteen sub-regions, which are listed and discussed below from roughly north to south.


The TTB finally approved American Viticultural Area (AVA) status for Calistoga in November 2009 after a long battle. While most of Napa Valley faces due south, Calistoga has a south-east aspect, creating large diurnal temperature variations that means the area is often the warmest in the valley during the day. Calistoga also has more annual rainfall than most of the valley, primarily during winter months, but less humidity on average.The soils here are of volcanic origin and are well-drained, varying from stoney loam to gravelly loam with some heavy silty loam soils towards in low-lying areas.

Howell Mountain

Located east of Calistoga in the Vaca Mountains, Howell Mountain is the country's 73rd AVA and the 1st Napa Valley sub-appellation approved. With elevation ranging between 1,400-2,200 feet, the region enjoys lower daytime temperatures than most of the valley. It also precludes the fog common in southern areas from reaching the vineyards here, meaning warmer summer nights that bring quicker and more even ripening and cooler spring temperatures that give it the latest bud break in Napa. Like Calistoga, Howell Mountain primarily has well-drained, volcanic soils and higher annual rainfall; its soils are rather infertile, which limits yields. 

Diamond Mountain District

The Diamond Mountain District runs along the eastern slopes of the Mayacamas Mountains, just south of Calistoga on the opposite side of the valley from Howell Mountain. The district's similar elevation to the Howell Mountain AVA gives it a similar climate, except its closer proximity to the ocean means even less diurnal temperature fluctuation. The Diamond Mountain District only has 500 acres planted to vines, seven wineries and thirteen growers. Soils here are a mix of volcanic and sedimentary, rather infertile and well-drained rocky loam to sandy loam.

Chiles Valley

The country's 133rd AVA, the Chiles Valley is located due south east from Howell Mountain. Since its relatively secluded, the area was not effected by phylloxera and has some of the oldest vineyards in California. Relatively warm days give way to cool nights, and the steep sides of the narrow valley force growers to plant along the valley floor. Harvest comes far later than nearby Oakville due to colder wintertime and springtime temperatures. Soils are of marine and alluvial origin; the valley floor is primarily fertile silty-clay, while hillsides are less fertile stony-clay.

Spring Mountain District

Similar climate to neighboring Diamond Mountain District but slightly cooler, resulting in a long growing season that extends far into November. This region is on the western slopes of the valley along the Mayacamas and has a unique mix of soil types; mostly sedimentary deposits mixed with some volcanic soils (in between the primarily volcanic Diamond Mountain District and primarily sedimentary Mt Veeder). This means well-drained and low fertility loam to sandy-loam soils.

St. Helena

St. Helena is one of Napa Valley's warmest sub-AVA's due to its location in a rather narrow section of the valley that produces higher radiative heat from hillside reflection. It is also well-protected by the mountains to the west, keeping it void of marine influence. Lying on the valley floor just below the the Spring Mountain District, it's not surprising that St. Helena's soils are quite similar in its southern and western areas; sedimentary in origin, gravely-clay with moderate drainage and fertility. Soils become deeper and more fertile moving north and east due to more volcanic influence.


Enjoys the most growing degree days of any Napa sub-AVA. The western bench area is cooler than the rest of the region with more marine influence and less afternoon sun. Mostly Deep, well-drained alluvial soils with high sandstone gravel content, which gives vineyards here good water retention and fertility. Soils become more volcanic as you move to the east, which are deeper and more fertile. 71% of total vineyard acreage in Rutherford is dedicated to Cabernet Sauvignon.


Oakville could be considered Napa Valley's most renowned sub-AVA, home to "cult Cabernet" producers and many of the biggest names in winemaking. It enjoys warm climate with high diurnal variation due to marine-influence fog. Oakville has similar soils to Rutherford, primarily sedimentary with more volcanic influence towards the east. 

Atlas Peak

Another of Napa's high-elevation districts that is void of nighttime fog. Atlas Peak has moderate temperatures and low diurnal variation, but its western orientation provides more direct sunlight to its vineyards. Very shallow, volcanic soils with poor water retention.


Cooler than up-valley regions due to marine influence, including foggy mornings and breezy afternoons. It's home to one of Napa's largest towns and over 4,000 acres of vineyards. It can be subject to dramatic diurnal temperature variation (can swing up to 40° F in one day). The soils are silt loam, relatively fertile and primarily of sedimentary and alluvial origin.

Stag's Leap District

Just east of Yountville, Stag's Leap District is tucked at the bottom of the Vaca Mountains. The rocky hillsides radiate significant heat here, creating much warmer temperatures than Yountville (regularly 10° F higher). Soil is combination of gravel loam and heavy clay mixed with rock.

Mount Veeder

Another sub-region in the Mayacamas Mountains above the fog line that enjoys moderate daytime temperatures and less diurnal temperature swing than the vallety floor. Its soils are of sedimentary origin, mostly shallow and well-drained sandy loam with low fertility. Known for its lower yields, its wines are typically well-structure and age-worthy. 

Oak Knoll District of Napa Valley

One of Napa's coolest regions due to proximity to San Pablo Bay, Oak Knoll District enjoys a long growing season. The marine influence provides morning fog that may linger through the day, and clearer summer conditions lead to high diurnal temperature differences. Soils are variable, largely originating from the Dry Creek alluvial fan, but more stoney volcanic soils in the northwestern area while the south and east (closer to San Pablo Bay) consist mainly of gravel loam and silty clay loam. Home to a mix of cool and warm climate grapes, and known for its more elegant styles of Chardonnay, Cabernet Sauvignon, and Merlot. 

Wild Horse Valley

This is one of 2 AVAs only partially contained with the Napa Valley AVA. Its eastern location keeps it slight warmer and its southern location provides it with high sunshine hours than most of Napa, while its proximity to Suisin Bay keeps its climate moderate. It is primarily planted with cooler climate grapes like Los Carneros.

Los Carneros

The southern most sub-region of Napa Valley stradles its border with Sonoma County AVA. Los Carneros enjoys a cooler marine climate with lower daytime temperatures thanks to ocean breezes through the Petaluma Gap to the west. Predominantly very shallow, clay soils that limit root depth and cause low yielding vines. Regional focus on Pinot Noir and Chardonnay.

Copyright © 2022 :: Michael Horton
Copyright © 2022 :: Michael Horton