Sonoma
The fog line, and what grows above and below it.
Sonoma is run by the cold Pacific. As the inland valleys heat up in the afternoon, they pull sea air in through every gap in the coast hills: the Petaluma Gap, the Russian River, the bay at Carneros. It arrives as wind in the afternoon and as fog in the evening, and it fills the low ground overnight before burning off inland the next morning.
That one engine sets everything else. The valley floors get hot afternoons and cold, foggy nights, so their day-to-night swing is wide, about 25 to 30°F, more on the hottest days. The coast ridges above the fog line, like Fort Ross-Seaview, which is drawn on the 920-foot contour for that reason, get cooler afternoons, milder nights and sun from early morning. Underneath the west of the county is Goldridge, a fine sandy soil left by an ancient sea.
Switch between fog, wind, and day and night to see the three faces of it. Our vineyards are on the map and on the chart beside it; tap any two to compare them and cut a slice through the hills between them.
Curve shapes are illustrative; the size of each swing is from published figures.
Every producer on this plate
Pick a producer to light up their vineyards and see where each wine comes from.
How the fog is drawn: the marine layer is modelled as a flat-topped sheet of cold air coming in from open water. It fills every low place it can reach without climbing over higher ground, out to a distance that follows the usual summer day. Real days vary, and the model ignores wind and warmth, so treat it as a picture of the pattern rather than a forecast.
Heights marked as the grower's figure come from our producer notes; others are read off the elevation data at the pin. Soil notes come from the producers' technical sheets.
Sources: elevation from AWS Terrain Tiles (USGS and other public data); AVA boundaries from the UC Davis Library AVA Digitizing Project.
On to Napa Valley · back to the United States.