The San Clemente 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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30° on Nov. 16, 2009, the coldest reading for this week of the year since 1968. Next is 31° in 2018.
San Clemente’s center stands about 230 ft above sea level. Within three miles the land runs from 10 ft to 760 ft, a difference of 750 ft: hilly country. Open water lies within three miles. The highest named summit within 15 miles is Sitton Peak, about 3,240 ft, 15 miles northeast.
Under the town center the state geologic map shows Miocene marine rocks (sandstone, mudstone), from the Oligocene to Pliocene, 2.6 to 34 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 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Mudstone, sandstone. Age: Paleocene to Oligocene, 23 to 66 million years old. About 5 mi of the line.
Felsic-volcanic, mafic-volcanic. Age: Late Jurassic to Early Cretaceous, 100 to 164 million years old. About 3 mi of the line.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 mi of the line.
Sandstone, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 0.4 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous to Late Cretaceous, 66 to 145 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.
Rain that falls on San Clemente runs only a short way, about 2 miles, to the Pacific Ocean.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of San Clemente; river miles along the main stem, rounded.
San Clemente has a cold desert climate. Summer afternoons average 83° in August; winter nights fall to about 38° in December. Barely 0.0 inches of rain fall in a normal year.
Normals 1991–2020 and records since 1968 at Camp Pendleton Mcas, 17 miles east-southeast, 160 ft lower. NOAA, through RCC-ACIS.
