The San Andreas 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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83° on Nov. 11, 2025, the hottest reading for this week of the year since 1992. Next is 82° in 2016.
San Andreas’s center stands about 1,070 ft above sea level. Within three miles the land runs from 750 ft to 2,330 ft, a difference of 1,580 ft: steep hill country. The highest named summit within 15 miles is Fort Mountain, about 3,300 ft, 15 miles northeast.
Under the town center the state geologic map shows Paleozoic metavolcanic rocks, unit 4 (Western Sierra Nevada Foothills), from the Paleozoic to Mesozoic, 66 to 542 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 7×. 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.
Slate, graywacke. Age: Triassic to Late Jurassic, 145 to 252 million years old. About 3 mi of the line.
Mafic-volcanic. Age: Jurassic, 145 to 202 million years old. About 3 mi of the line.
Andesite. Age: Late Oligocene to Pleistocene, 2 to 24 million years old. About 2 mi of the line.
Sandstone, conglomerate. Age: Oligocene to Pleistocene, less than 34 million years old. About 2 mi of the line.
Metavolcanic. Age: Paleozoic to Mesozoic, 66 to 542 million years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 3 smaller units along the line are not listed.
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 San Andreas reaches San Francisco Bay and the Pacific Ocean by way of San Andreas Creek, the Calaveras, the San Joaquin and New York Slough: about 95 river miles.
Lake on the way: New Hogan Lake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of San Andreas; river miles along the main stem, rounded.
San Andreas has a hot-summer Mediterranean climate. Summer afternoons average 97° in July; winter nights fall to about 38° in January. About 30 inches of rain fall in a normal year.
On November 14 San Andreas normally reaches 66° and falls to 45°. The record high is 81°, in 1999; the record low 37°, in 2022. The most rain on this date, 2.12 in, fell in 2025.
Normals 1991–2020 and records since 1992 at New Melones Dam Headquarters, 16 miles southeast, 110 ft lower. NOAA, through RCC-ACIS.
