The Diablo Grande 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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89° on Nov. 11, 1921, the hottest reading for this week of the year since 1902. Next is 86° in 2019.
Diablo Grande’s center stands about 1,050 ft above sea level. Within three miles the land runs from 810 ft to 2,290 ft, a difference of 1,480 ft: steep hill country. The highest named summit within 15 miles is Mount Stakes, about 3,780 ft, 10 miles west-southwest.
Under the town center the state geologic map shows Upper Cretaceous marine rocks, unit 1 (Upper Great Valley Sequence) (sandstone, siltstone-mudstone), from the Late Cretaceous, 66 to 100 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 6×. 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, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 7 mi of the line.
Melange. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 6 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 6 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 0.7 mi of the line.
Greenstone. Age: Jurassic to Cretaceous, 66 to 202 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. 2 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 Diablo Grande reaches San Francisco Bay and the Pacific Ocean by way of Salado Creek, the San Joaquin and New York Slough: about 110 river miles.
90 miles of the trip are on the San Joaquin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Diablo Grande; river miles along the main stem, rounded.
Diablo Grande has a hot semi-arid climate. Summer afternoons average 100° in July; winter nights fall to about 38° in January. About 12 inches of rain fall in a normal year.
On November 14 Diablo Grande normally reaches 71° and falls to 43°. The record high is 83°, in 1921; the record low 21°, in 1916. The most rain on this date, 1.25 in, fell in 1965.
Normals 1991–2020 and records since 1902 at Newman, 16 miles east-southeast, 960 ft lower. NOAA, through RCC-ACIS.
