Sonoma is cooler than Napa. Yep, I said it. The climate is more moderate, and the people are super chill. You are far more apt to have a Sonoma producer discuss their favorite varietal paired with their favorite strain of weed. Sonoma feels less commercial than Napa also, more organic style, farmers that have grown into wine production, even if it has been generations in the making. Chardonnay is the principle grape in the region, but many reds are produced here also. The reds, comprising two-thirds of the wine production, are Pinot Noir, Cabernet Sauvignon, Zinfandel, and some Merlot many more as well, but these represent the greatest acreage. Sonoma has several AVA's, they are parceled based off soil composition and microclimate. The effect of the distribution of cool air determines grape selection and they vary widely site to site. If you read my post a couple days ago about Napa Valley, I took the reader through the valley south to north, today we will go south through Sonoma County.
Sonoma has 60 miles of coastline, and the cool air from the ocean is liberally distributed through the Russian River Valley and the Coastal Range.In the north of Sonoma, high on a ridge above Lake Sonoma we find Rockpile AVA. The elevation of Rockpile allows for sunny days that warm area and allows for the production of Zinfandel, which also thrives directly south, in the Dry Creek Valley AVA, where it has been produced continuously for over 100 years. On the hills of Dry Creek, one will also find Cabernet Sauvignon and Merlot, and on Dry Creek Valley's floor, where it is cooler, Sauvignon Blanc is planted.
To the east, along the foothills of the Mayacamas, which separate Napa from Sonoma, Cabernet Sauvignon is planted. Both Alexander Valley AVA, and Knights Valley AVA face west on the foothills and get plenty of sun exposure on the foothills above the fog. Opposite the Mayacamas Range, to the west, the Sonoma Coast AVA is far cooler, the ocean creates heavy fog, which can take half the day to burn off, also relatively high rainfall. The Sonoma Coast AVA is home to Pinot Noir, Chardonnay, and what the California producers call "cool-climate" Syrah. Being from Minnesota, cool climate has a relative meaning.
The Russian River Valley AVA is a cooler climate area as well, where the river cuts through the Coast Range and allows cooler ocean breezes to temper the valley. Pinot Noir and Chardonnay thrive here, and because the region is so optimum for climate many producers source single vineyard fruit to showcase the very specific terroirs. Two sub-appellations, Green Valley, and Chalk Hill AVA, which takes it's name from the high concentration of chalky, volcanic soil which makes great Chardonnay, but don't neglect the Sauvignon Blanc produced here either!
The Sonoma Valley AVA is situated between the Mayacamas and the Sonoma Mountains to the west, sheltered from the coastal cool breezes, but the San Pablo Bay does allow some cooling influence up the Sonoma Creek. The area contains some sub-appellations, Sonoma Mountain AVA, Moon Mountain District AVA, Bennett Valley AVA, and the Sonoma portion of Los Carneros falls within the boundaries as well. The elevations vary widely, as do the soil compositions, and thus the grapes planted. Chardonnay and Pinot Noir dominate the plantings though, and are frequently harvested early for sparkling wine production.
Sonoma, like Napa, is very diverse in climate, elevation, soil composition, and winemaking styles. As an educator it offers me huge variety in engineering a curriculum. I have several friends who produce in the region, and we can build any type of wine class you would like. Let me know what you want to try.