The French 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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22° on Nov. 17, 1958, the coldest reading for this week of the year since 1897. Next is 25° in 1964.
French Valley’s center stands about 1,370 ft above sea level. Within three miles the land runs from 1,280 ft to 2,140 ft, a difference of 860 ft: hilly country. The highest named summit within 15 miles is Agua Tibia Mountain, about 4,750 ft, 15 miles south-southeast.
Under the town center the state geologic map shows Jurassic marine rocks, unit 4 (Peninsular Ranges and Western Transverse Ranges) (argillite), from the Paleozoic to Late Jurassic, 145 to 542 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 11×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Tonalite. Age: Middle Jurassic to Late Cretaceous, 66 to 175 million years old. About 10 mi of the line.
Argillite. Age: Paleozoic to Late Jurassic, 145 to 542 million years old. About 5 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 4 mi of the line.
Diorite, gabbro. Age: Triassic to Cretaceous, 66 to 252 million years old. About 3 mi of the line.
Plutonic, gneiss. Age: Paleoproterozoic to Late Cretaceous, 66 to 2,500 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 0.4 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.
A raindrop that lands in French Valley reaches the Pacific Ocean by way of Warm Springs Creek, Murrieta Creek and the Santa Margarita: about 45 river miles.
Often dry. About 40% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of French Valley; river miles along the main stem, rounded.
French Valley has a hot semi-arid climate. Summer afternoons average 98° in August; winter nights fall to about 40° in December. About 12 inches of rain fall in a normal year.
On November 14 French Valley normally reaches 74° and falls to 46°. The record high is 94°, in 1906; the record low 25°, in 1964. The most rain on this date, 0.97 in, fell in 1944.
Normals 1991–2020 and records since 1897 at Elsinore, 15 miles west-northwest, 100 ft lower. NOAA, through RCC-ACIS.
