Diamond Mountain District
Sub-AVA · Napa County · District 4 — 99.47% of this appellation; also in Sonoma (0.53%)
27 CFR 9.166 · established 2001-06-01
Heat class IV · 1991-2020 normals
Climate normals in three numbers
, Apr 1 – Oct 31
7 GridMET cells cover this region
raw 4 km GridMET would say III
season rain, Apr 1 – Oct 31
53 mm of it in the , Sep 1 – Oct 31
Warm and cool vintages since 1980
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Rain across the season, and at harvest
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The boundary
Hovering a shaded region names it; a click opens its page.
Measured vineyard area
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Drought categories, year by year
Napa County — not Diamond Mountain District
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What's in the ground
5.9
pH, 1:1 water
13.8cm
, whole profile
88cm
to
Well drained
, dominant condition
Distribution across 27 · mean ◆, median │, p10–p90 bar
Dominant
- 55.9%
- 15.3%
- 13.4%
- 10.6%
- 3.4%
27 map units · soil described over 95.3% of the region’s area · 10.0% is water, rock outcrop or other non-soil · 96% of the described area has a restrictive layer within the profile.
Sand, silt and clay, against every other appellation
Loam
36% sand · 46% silt · 17% clay
Sandier than 22% of California appellations and clayier than 16%. Each grey point is one appellation’s topsoil; appellations nest, so this is a distribution of places rather than of land.
Plus 13% rock fragments by volume, which the triangle does not describe — the three fractions are of the fine-earth material only.
Elevation, slope and aspect
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Producers
A curated roster, not a census — only source-verified entries appear, 2772 published across the atlas.
Bearing acreage by variety
Napa County · District 4 — 99.47% of this appellation; also in Sonoma (0.53%)
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Price per ton
Napa County · District 4 — 99.47% of this appellation; also in Sonoma (0.53%)
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The appellation in federal law
The boundary, in the government’s own words (235 words)
(c) Boundaries. The viticultural area is located in Napa County, California. The beginning point is where the boundary between Napa and Sonoma counties intersects Petrified Forest Road in Section 3 of Township 8 North, Range 7 West, Mount Diablo Base and Meridian on the Mark West Springs map; (1) Then north and east along Petrified Forest Road approximately 1.9 miles to the point where it intersects the 400-foot contour just east of Section 35 of Township 9 North, Range 7 West, Mount Diablo Base and Meridian, in the Mallacomes land grant; (2) Then generally east southeast along the 400-foot contour approximately 6.5 miles to the point where it intersects Ritchey Creek in Section 3 of Township 8 North, Range 6 West, Mount Diablo Base and Meridian; (3) Then west southwest along Ritchey Creek approximately 2.2 miles to the point where it intersects the boundary between Sections 17 and 20 of Township 8 North, Range 6 West, Mount Diablo Base and Meridian; (4) Then due west in a straight line along the section boundary approximately 0.8 miles to the point where it intersects the boundary between Napa and Sonoma Counties between Sections 18 and 19 of Township 8 North, Range 6 West, Mount Diablo Base and Meridian; (5) Then generally northwest along the boundary between Napa and Sonoma Counties approximately 4.2 miles to the point where it intersects Petrified Forest Road, to the point of beginning.