The Napa plate. Relief from Copernicus GLO-30; rivers and lakes from USGS NHD; watersheds from the USGS Watershed Boundary Dataset; roads and city limits from Census TIGER 2024.
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3.27 inches of rain fell in two days, the most for this week of the year since records began in 1893. The next wettest, 3.07 inches, fell in 1942.
Napa’s center stands about 30 ft above sea level. Within three miles the land runs from 0 ft to 430 ft, a difference of 430 ft: hilly country. The highest named summit within 15 miles is Mount Vaca, about 2,800 ft, 12 miles northeast.
Under the town center the state geologic map shows Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 10×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 8 mi of the line.
Dacite. Age: Late Miocene to Late Pliocene, 3 to 7 million years old. About 7 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous, 113 to 145 million years old. About 3 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 3 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
Heights from Copernicus GLO-90 (a surface model: it includes buildings and tree canopy); summits from USGS GNIS; rivers from USGS NHDPlus HR; rock from the USGS State Geologic Map Compilation.
A raindrop that lands in Napa reaches San Francisco Bay and the Pacific Ocean by way of the Napa: about 18 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Napa; river miles along the main stem, rounded.
Napa has a warm-summer Mediterranean climate. Summer afternoons average 84° in August; winter nights fall to about 40° in January. About 27 inches of rain fall in a normal year.
On November 14 Napa normally reaches 67° and falls to 44°. The record high is 86°, in 2008; the record low 28°, in 1978. The most rain on this date, 1.70 in, fell in 1972.
Normals 1991–2020 and records since 1893 at Napa State Hospital, here. NOAA, through RCC-ACIS.
