The San Carlos 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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3.29 inches of rain fell in two days, the most for this week of the year since records began in 1906. The next wettest, 3.22 inches, fell in 1981.
San Carlos’s center stands about 30 ft above sea level. Within three miles the land runs from 0 ft to 800 ft, a difference of 800 ft: hilly country. The highest named summit within 15 miles is Black Mountain, about 2,810 ft, 14 miles south-southeast.
Under the town center the state geologic map shows Older Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene, less than 2.6 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.
Mudstone, sandstone. Age: Paleocene to Oligocene, 23 to 66 million years old. About 5 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 3 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 2 mi of the line.
Sandstone, mudstone. Age: Miocene to Pleistocene, less than 23 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 1 mi of the line.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 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.
Rain that falls on San Carlos runs straight into San Francisco Bay and the Pacific Ocean.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of San Carlos; river miles along the main stem, rounded.
San Carlos has a warm-summer Mediterranean climate. Summer afternoons average 81° in July; winter nights fall to about 40° in January. About 19 inches of rain fall in a normal year.
On November 14 San Carlos normally reaches 65° and falls to 44°. The record high is 79°, in 2010; the record low 29°, in 1935. The most rain on this date, 1.72 in, fell in 1953.
Normals 1991–2020 and records since 1906 at Redwood City, 2 miles south-southeast. NOAA, through RCC-ACIS.
