The Alhambra Valley 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. 15, 2008, the hottest reading for this week of the year since 1970. Next is 81° in 2010.
Alhambra Valley’s center stands about 360 ft above sea level. Within three miles the land runs from 90 ft to 1,330 ft, a difference of 1,240 ft: steep hill country. The highest named summit within 15 miles is Mount Diablo, about 3,810 ft, 13 miles east-southeast.
Under the town center the state geologic map shows Paleocene marine rocks, unit 1 (Central and Southern California) (sandstone, mudstone), from the Paleocene, 56 to 66 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 9×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 8 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 5 mi of the line.
Sandstone, mudstone. Age: Paleocene, 56 to 66 million years old. About 3 mi of the line.
Greenstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 2 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous to Late Cretaceous, 66 to 145 million years old. About 1 mi of the line.
Siltstone-mudstone. Age: Late Jurassic to Early Cretaceous, 100 to 164 million years old. About 0.6 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 Alhambra Valley reaches San Francisco Bay and the Pacific Ocean by way of the Arroyo del Hambre: about 5 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alhambra Valley; river miles along the main stem, rounded.
Alhambra Valley has a warm-summer Mediterranean climate. Summer afternoons average 75° in September; winter nights fall to about 45° in January. About 23 inches of rain fall in a normal year.
On November 14 Alhambra Valley normally reaches 66° and falls to 50°. The record high is 82°, in 2008; the record low 37°, in 1978. The most rain on this date, 0.82 in, fell in 1972.
Normals 1991–2020 and records since 1970 at Oakland Museum, 14 miles south-southwest, 330 ft lower. NOAA, through RCC-ACIS.
