The Johnsville 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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3.25 inches of rain fell in two days, the most for this week of the year since records began in 1915. The next wettest, 3.16 inches, fell in 1981.
Johnsville’s center stands about 5,180 ft above sea level. Within three miles the land runs from 4,480 ft to 7,310 ft, a difference of 2,830 ft: mountain country. The highest named summit within 15 miles is Sierra Buttes, about 8,430 ft, 12 miles south-southeast.
Under the town center the state geologic map shows Quaternary glacial deposits (coarse-detrital), from the Pleistocene, less than 2.6 million years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Argillite, quartzite, phyllite. Age: Ordovician to Triassic, 202 to 487 million years old. About 9 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 7 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 3 mi of the line.
Andesite. Age: Devonian to Permian, 252 to 422 million years old. About 3 mi of the line.
Andesite, basalt. Age: Late Oligocene to Pleistocene, 2 to 24 million years old. About 2 mi of the line.
Mafic-volcanic, felsic-volcanic. Age: Permian to Jurassic, 145 to 260 million years old. About 0.3 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 Johnsville reaches San Francisco Bay and the Pacific Ocean by way of Eureka Creek, Jamison Creek, the Middle Fork Feather, the Feather and the Sacramento: about 220 river miles.
75 miles of the trip are on the Sacramento.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Johnsville; river miles along the main stem, rounded.
Johnsville has a dry-summer warm-summer continental climate. Summer afternoons average 86° in July; winter nights fall to about 19° in January. A normal year brings about 38 inches of snow; with the rain, that comes to about 23 inches of water.
On November 14 Johnsville normally reaches 53° and falls to 24°. The record high is 74°, in 1929; the record low −1°, in 1915. The most rain on this date, 1.15 in, fell in 1952.
Normals 1991–2020 and records since 1915 at Portola, 12 miles east-northeast, 330 ft lower. NOAA, through RCC-ACIS.
