The Las Flores 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.
Las Flores’s center stands about 700 ft above sea level. Within three miles the land runs from 320 ft to 1,020 ft, a difference of 700 ft: hilly country. The highest named summit within 15 miles is Santiago Peak, about 5,660 ft, 10 miles north-northeast.
Under the town center the state geologic map shows Oligocene nonmarine rocks, unit 2 (Central and Southern California) (sandstone, conglomerate), from the Middle Eocene to Early Miocene, 16 to 48 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 4×. 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, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 5 mi of the line.
Sandstone, conglomerate. Age: Middle Eocene to Early Miocene, 16 to 48 million years old. About 5 mi of the line.
Argillite. Age: Paleozoic to Late Jurassic, 145 to 542 million years old. About 4 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 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, mudstone. Age: Miocene to Pleistocene, less than 23 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 Las Flores reaches the Pacific Ocean by way of the Arroyo Trabuco, Trabuco Creek and San Juan Creek: about 10 river miles.
Often dry. About 100% 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 Las Flores; river miles along the main stem, rounded.
Las Flores 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 Las Flores 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, 690 ft lower. NOAA, through RCC-ACIS.
