The San Juan Capistrano 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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34° on Nov. 17, 1958, the coldest reading for this week of the year since 1921. Next is 37° in 1938.
San Juan Capistrano’s center stands about 110 ft above sea level. Within three miles the land runs from 40 ft to 910 ft, a difference of 870 ft: hilly country. The highest named summit within 15 miles is Sugarloaf, about 3,260 ft, 13 miles 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 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.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 6 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 3 mi of the line.
Coarse-detrital. Age: Pleistocene, 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 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.
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 San Juan Capistrano reaches the Pacific Ocean by way of San Juan Creek: about 3 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of San Juan Capistrano; river miles along the main stem, rounded.
San Juan Capistrano has a cold semi-arid climate. Summer afternoons average 74° in September; winter nights fall to about 50° in January. About 9 inches of rain fall in a normal year.
On November 14 San Juan Capistrano normally reaches 69° and falls to 55°. The record high is 81°, in 1940; the record low 39°, in 1938. The most rain on this date, 1.11 in, fell in 1944.
Normals 1991–2020 and records since 1921 at Newport Beach Harbor, 15 miles west-northwest, 100 ft lower. NOAA, through RCC-ACIS.
