The San Luis Obispo 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, 1998, the coldest reading for this week of the year since 1893. Next is 31° in 1982.
San Luis Obispo’s center stands about 240 ft above sea level. Within three miles the land runs from 110 ft to 1,510 ft, a difference of 1,400 ft: steep hill country. The highest named summit within 15 miles is Hi Mountain, about 3,170 ft, 13 miles east.
Under the town center the state geologic map shows Franciscan Complex, unit 1 (Coast Ranges) (sandstone, mudstone), from the Jurassic to Cretaceous, 66 to 202 million years old.
The section below crosses 10 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.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 7 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 4 mi of the line.
Serpentinite. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 4 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous, 113 to 145 million years old. About 3 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 1 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 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. 4 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 Luis Obispo reaches the Pacific Ocean by way of San Luis Obispo Creek: about 8 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of San Luis Obispo; river miles along the main stem, rounded.
San Luis Obispo has a warm-summer Mediterranean climate. Summer afternoons average 80° in August; winter nights fall to about 44° in January. About 22 inches of rain fall in a normal year.
On November 14 San Luis Obispo normally reaches 71° and falls to 48°. The record high is 88°, in 2021; the record low 33°, in 1929. The most rain on this date, 2.67 in, fell in 1972.
Normals 1991–2020 and records since 1893 at San Luis Obispo Poly, here. NOAA, through RCC-ACIS.
