The Banning 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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93° on Nov. 15, 1999, the hottest reading for this week of the year since 1948. Next is 92° in 1989.
Banning’s center stands about 2,340 ft above sea level. Within three miles the land runs from 2,010 ft to 3,710 ft, a difference of 1,700 ft: steep hill country. The highest named summit within 15 miles is San Gorgonio Mountain, about 11,470 ft, 12 miles north-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 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 2×. 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.
Gneiss. Age: Paleoproterozoic to Miocene, 5.3 to 2,500 million years old. About 7 mi of the line.
Tonalite. Age: Middle Jurassic to Late Cretaceous, 66 to 175 million years old. About 4 mi of the line.
Plutonic, gneiss. Age: Paleoproterozoic to Late Cretaceous, 66 to 2,500 million years old. About 3 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 1 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 0.8 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 Banning reaches Salton Sea by way of Smith Creek, the San Gorgonio and the Whitewater: about 65 river miles. Salton Sea has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Banning; river miles along the main stem, rounded.
Banning has a hot semi-arid climate. Summer afternoons average 97° in August; winter nights fall to about 39° in December. About 12 inches of rain fall in a normal year.
On November 14 Banning normally reaches 73° and falls to 45°. The record high is 91°, in 2021; the record low 30°, in 2000. The most rain on this date, 0.29 in, fell in 1997.
Normals 1991–2020 and records since 1948 at San Jacinto, 11 miles south-southwest, 820 ft lower. NOAA, through RCC-ACIS.
