Los Carneros AVA Climate: Cool, with prevailing marine air from San Pablo Bay; high temps rarely exceed 80°F (27°C); less diurnal variation Elevation: Sea level to 700 ft (214 m) Rainfall: Lowest in Napa Valley – 18 to 24 inches (45.7 to 61 cm) annually Soils: Clay dominated, shallow, more loam and hillside alluvials in the northern section; yields typically restrained by the hard claypan subsoil, which prevents deep rooting Principal varieties: Chardonnay, Merlot, Pinot Noir

Coombsville Climate: Temperate climate moderated by near-proximity to the San Francisco Bay and the influences of marine air Elevation: Most vineyards are in the 100-500 foot (30-150 m) zone, though a small portion tops 1000 feet (300 m) Rainfall:  Average rainfall is 24.6 inches (62 cm) per year over the last 100 years Soils: Primarily weathered volcanic rock and alluvial deposits from the Vaca Range that surrounds the region Principal varieties: Dominated by Cabernet Sauvignon on the hillsides with Merlot, Chardonnay, Syrah and Pinot Noir in the lower, cooler sites

Oak Knoll District of Napa Valley AVA Climate: Moderate to cool with morning fall; late afternoon breezes and slightly cooler temperatures than upper valley; temperatures may reach 90°F (32.2°C) and drop to around 50°F (10°C) at night Elevation: Sea level to 800 ft (244 m) Rainfall: 36 inches (91 cm) annually Soils: The valley’s largest alluvial fan formed by Dry Creek; northwest area is composed of volcanically derived soils, with stony or gravelly consistency; south and east areas transition from gravel to silty clay loam Principal varieties: Merlot, Cabernet Sauvignon, Chardonnay

Yountville AVA Climate: Moderate, with marine influence and fog; cool summer mornings and breezes keep afternoons comfortable; peak temperatures may reach 90°F (32.2°C), with noticeable diurnal fluctuation to the mid-50°F range (13°C) Elevation: Sea level to 1100 ft (335 m) Rainfall: 32 inches (81 cm) annually Soils: Principally gravelly silt loams, sedimentary in origin, and gravelly alluvial soils with rock, moderately fertile Principal varieties: Cabernet Sauvignon, Merlot

Stags Leap District AVA Climate: Moderately warm, afternoon marine winds which cool the warmer air radiating off the bare rocks of the surrounding hillsides; often warmer than neighboring Yountville AVA, reaching the mid-90°F range (35°C) Elevation: 66 to 400 ft (20 to 122 m) Rainfall: 30 inches (76 cm) annually Soils: Volcanic gravel-loams on the floor, with rocky hillsides, and low-to moderate fertility due to hard clay bedrock sub-soils Principal varieties: Cabernet Sauvignon, Merlot, Sangiovese, Chardonnay, Sauvignon Blanc

Oakville AVA Climate: Moderately warm, temperatures can reach the mid-90°F (35°C), but also strongly affected by fog, which helps keep acidity levels good; east side of the AVA receives more of the warmer afternoon sun Elevation: 75 to 500 ft (23 to 152 m) Rainfall: 35 inches (89 cm) annually Soils: Primarily sedimentary gravelly alluvial loams on the west, with more volcanic but heavier soils on the east; kow-to-moderate fertility and fairly deep Principal varieties: Cabernet Sauvignon, Merlot, Sauvignon Blanc

Rutherford AVA Climate: Moderately warm, somewhat influenced by fog; western bench cooler, with less late afternoon sun; summer peak temperatures are mid-90°F (35°C) with good diurnal range Elevation: 100 to 500 ft (30 to 152 m) Rainfall: 38 inches (97 cm) annually Soils: West side is sedimentary, gravelly-sandy and alluvial, with good water retention and moderate fertility; east side has more volcanic soils, moderately deep, more fertile Principal varieties: Cabernet Sauvignon, Merlot, Cabernet Franc, Zinfandel

St. Helena AVA Climate: Warm, due to protection from hills; less fog and wind; narrowing of the valley floor provides more heat reflection off the hillsides; temperatures can peak in the mid-to-high 90°F range (35° to 37°C) Elevation: 150 to 600 ft (46 to 183 m) Rainfall: 38 to 40 inches (97 to 102 cm) annually Soils: South and west borders are more sedimentary, gravel-clay soils, with lower fertility and moderate water retention; to the north and east, soils are prevalently volcanic in origin and are deeper and more fertile Principal varieties: Cabernet Franc, Cabernet Sauvignon, Merlot, Syrah, Viognier, Zinfandel

Spring Mountain District AVA Climate: Noted for steeper, smaller hillside vineyards surrounded by tall evergreen forest; cooler daytime temperatures than valley floor, generally not exceeding 85°F (29.4°C) Elevation: 400 to 2200 ft (122 to 671 m) Rainfall: 50 inches (127 cm) annually Soils: Primarily sedimentary: weathered sandstone/shale, loamy and friable in texture; drainage is high, fertility low Principal varieties: Cabernet Sauvignon, Merlot, Zinfandel, Chardonnay, Viognier

Diamond Mountain District AVA Climate: Moderately warm temperatures with lower maximums and higher minimums temperatures than the north Elevation: 400 to 1800 ft (122 to 549 m) Rainfall: 50 to 55 inches (127 to 140 cm) annually Soils: Residual uplifted soils of volcanic origin, often reddish and very fine grained, even gritty in texture, composed of both weathered sedimentary and volcanic origin Principal varieties: Cabernet Sauvignon, Cabernet Franc

Howell Mountain District AVA Climate: Generally above marine layer; slightly warmer and drier than across the valley, with strong afternoon sun; summer temperatures range from 55°F to the high 90°F (13° to 37°C); cool nights help maintain good acidity Elevation: 600 to 2200 ft (183 to 671 m) Rainfall: 42 inches (107 cm) annually Soils: Predominantly volcanic, shallow and infertile; drainage is high, fertility low Principal varieties: Cabernet Sauvignon, Merlot, Zinfandel, Viognier

Mount Veeder AVA Climate: Cool to moderate, with most vineyards above the fog line; warmer nights and cooler days than valley floor; typical mid-summer high temperatures top out at about 85°F (30°C) Elevation: 500 to 2600 ft (153 to 793 m) Rainfall: 45 inches (114.3 cm) annually Soils: Sedimentary based, shallow and generally well-drained, as well as more acidic, with low fertility; most have a sandy-loam texture Principal varieties: Cabernet Sauvignon, Merlot, Zinfandel, Chardonnay

Atlas Peak AVA Climate: Cool, mountain-influenced, with temperatures about 10° to 15°F cooler than valley floor in summer; above the fog line; low diurnal change, with summer temperatures rarely above 90°F (32.2°C) Elevation: 400 to 2600 ft (122 to 793 m) Rainfall: 34 inches (86 cm) annually Soils: Volcanic in origin, with basaltic red color, shallow with limited water retention; irrigation is often essential Principal varieties: Cabernet Sauvignon, Chardonnay

Chiles Valley District AVA Climate: Warmer summer days, mid-80s°F plus (29.4°C), but due to higher elevation and fog that forms after sunset, falls to 50°F (10°C) or lower at night; colder winters and spring, with strong winds; harvest comes later Elevation: 600 to 1200 ft (183 to 370 m) Rainfall: 35 inches (88 cm) annually Soils: Floor is primarily alluvial soils with silty-clay composition of marine origin, with good fertility; hillsides show more clay-loam and stony-clay composition, mostly marine in origin, with some volcanic outcropping, and less fertility Principal varieties: Cabernet Sauvignon, Cabernet Franc, Merlot

Calistoga AVA Climate: Warm to hot, depending upon time of year; lower humidity; summer temperatures peak to 90°F (32.2°C) and fall to low 50s°F (11°C), the result of marine air from the northwest; cool afternoon and evening breezes Elevation: 300 to 1200 ft (92 to 370 m) Rainfall: 38 to 60 inches (96.5 to 150 cm) annually Soils: Almost completely of volcanic origin, soils range from rocky, stony loam on the hillsides, to gravelly or cobbly loams on the alluvial fans, to heavier clay-slit soils in the valley center areas Principal varieties: Cabernet Sauvignon, Zinfandel, Syrah, Petite Sirah

Wild Horse Valley AVA Climate: A warmer area well to the east, but still moderated by both altitude and prevailing winds coming off Suisun Bay to the southeast. Elevation: 600 to 1900 ft (186 to 589 m) Rainfall: 31 inches (79 cm) annually Soils: The parent material consists primarily of sedimentary and igneous sources. Most of the soils are shallow with limited water retention, so irrigation is often essential Principal varieties: Cabernet Sauvignon, Pinot Noir and Chardonnay