Being only 30 miles long and several miles wide, California’s Napa Valley American Viticultural Area (AVA) is one of the smallest winegrowing regions in the world, with only one-sixth the planted acreage of Bordeaux. About 95% of the wineries are family-owned businesses. The region’s established viticultural practices result in low yields of high-quality grapes, from which the winemakers produce Napa Valley’s renowned wines, which include Cabernet Franc, Cabernet Sauvignon, Merlot, Pinot Noir, Zinfandel, Chardonnay and Sauvignon Blanc. Napa generates only 4% of California’s wine grape harvest but has an extraordinary mixture of microclimates, weather and geography, as well as some of the most varied soils found in a wine region anywhere.

In 1968 Napa Valley became the home of the first Agricultural Preserve in the U.S., a long time before environmental issues became a major concern. Today it has the most comprehensive and stringent land use and environmental regulations of any American winegrowing region.

Napa contains 16 sub or nested appellations, each with its own distinct microclimate and terrain that provide recognizable characteristics on the grapes grown there. These sub appellations are presented alphabetically below:

Atlas Peak

The elevation ranges between 230 to 800 metres above sea level with temperatures in the summer that are about 10–15° cooler than the valley floor. There is low day-to-night temperature range, with summer temperatures rarely rising above 32° Celsius.

Cabernet Sauvignon and Chardonnay grapes are grown in this region.

Calistoga

Daytime summer temperatures may reach more than 38° Celsius and fall to as low as 4° at night. There are cool afternoon and evening breezes. Elevations range from 90 to 370 metres above sea level.

The main varietals grown in this area are Cabernet Sauvignon, Zinfandel, Syrah and Petite Sirah.

Chiles Valley

Temperatures peak in the 25° range but the higher elevation and summer fog at night result in nighttime temperatures in the 10° range.  With an elevation of 180 to 370 metres above sea level, there are colder winters and springs, as well as strong winds, which results in the harvest coming later than down in the valley.

The key varietals are Cabernet Sauvignon, Merlot and Cabernet Franc.

Coombsville

Because of the cool maritime winds from the San Pablo Bay, as well as the Petaluma Gap, high temperatures rarely get above 27° Celsius. This appellation is at a low elevation not exceeding 200 metres above sea level.

The grape varietals include Pinot Noir, Merlot and Chardonnay.

Diamond Mountain

There are moderately warm temperatures in this region, with less fluctuation than the north Napa Valley floor. Summertime temperatures range from 10° t0 30° Celsius. The elevation ranges from 120 to 670 metres above sea level.

Cabernet Sauvignon and Cabernet Franc varietals are grown in the region.

Howell Mountain

Howell Mountain is situated above the fog line on the eastern side of the valley. This area is warmer and drier than the other appellations because of more hours of sunshine and an insignificant amount of marine influence. The elevation ranges from 180 to 800 metres above sea level.

Cabernet Sauvignon, Merlot and Zinfandel grapes are grown in this area.

Los Carneros 

With marine winds from the San Pablo Bay and the Petaluma Gap, high temperatures rarely exceed 27° Celsius. Elevations range from sea level to 215 metres above sea level.

Varietals grown include Pinot Noir, Merlot and Chardonnay.

Mount Veeder

There is a cool to moderate temperature in this region, with most of the vineyards situated above the fog line. This results in warmer nights and cooler days than on the valley floor below. Normal summer highs are in the 30° Celsius range. Elevation ranges from 150 to 800 metres above sea level.

Cabernet Sauvignon, Merlot, Zinfandel and Chardonnay grapes are grown.

Oak Knoll

Having a moderate to cool climate with marine air and fog often remaining until late morning, afternoon breezes often develop, maintaining summer temperatures that reach as high as 33° Celsius. Elevations rise from sea level up to 150 metres.

The varietals include Cabernet Sauvignon, Merlot, Chardonnay and Sauvignon Blanc.

Oakville

The climate is moderately warm, with temperatures generally in the mid-30s during summer, but are impacted by night and early morning fog. Elevations are the same as Oak Knoll, rising from sea level to 150 metres.

However, only Cabernet Sauvignon, Merlot and Sauvignon Blanc varietals produced here.

Rutherford

The region is moderately warm, marginally influenced by early morning fog. Summer temperatures usually rise to the mid-30s, with a distinct day-to-night fluctuation in temperature. Elevations range from sea level to 180 metres.

Grape varietals include Cabernet Sauvignon, Merlot, Cabernet Franc and Zinfandel.

St. Helena

Less fog and wind, along with heat reflecting off the hillsides, see summer temperatures often reach the mid-to-high 30s. Elevations range from 30 to 200 metres above sea level.

Grape grown include Cabernet Sauvignon, Cabernet Franc, Merlot, Syrah and Zinfandel.

Spring Mountain

Cool weather prevails as most of the vineyards are located above the fog line, providing warmer nights and cooler days than the valley floor below. Mid-summer temperatures reach 30° Celsius. Elevations range from 180 to 800 metres above sea level.

Grapes grown include Cabernet Sauvignon, Merlot, Cabernet Franc, Chardonnay and Zinfandel

Stags Leap

This region is moderately warm with afternoon marine winds cooling the warmer air. Summer temperatures can reach to about 40° Celsius but are normally in the mid-30s. Elevations range from sea level to 150 metres.

Grapes grown include Cabernet Sauvignon, Merlot, Chardonnay and Sauvignon Blanc.

Wild Horse Valley

This is one of the warmer regions with summer temperatures hovering in the mid-30s. Elevations range from 180 to 600 metres above sea level.

Varietals include Cabernet Sauvignon, Pinot Noir and Chardonnay.

Yountville

Moderate, with cool marine influence and morning fog, summer mornings are cool in this region. Marine breezes keep afternoons more comfortable than further up the valley with high temperatures reaching 32° Celsius and nighttime lows dropping into the teens. Elevations range from just above sea level to 60 metres.

Varietals are limited to Cabernet Sauvignon and Merlot.

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