The Cotati 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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91° on Nov. 17, 1932, the hottest reading for this week of the year since 1893. Next is 85° in 1923.
Cotati’s center stands about 110 ft above sea level. Within three miles the land runs from 80 ft to 430 ft, a difference of 350 ft: rolling country. The highest named summit within 15 miles is Mount Hood, about 2,720 ft, 12 miles northeast.
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 6 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: Miocene to Pleistocene, less than 23 million years old. About 9 mi of the line.
Dacite. Age: Late Miocene to Late Pliocene, 3 to 7 million years old. About 8 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 2 mi of the line.
Andesite, dacite. Age: Middle Miocene to Late Miocene, 9.5 to 13 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.
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 Cotati reaches the Pacific Ocean by way of the Laguna de Santa Rosa, Mark West Creek and the Russian: about 45 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Cotati; river miles along the main stem, rounded.
Cotati has a warm-summer Mediterranean climate. Summer afternoons average 82° in September; winter nights fall to about 38° in December. About 26 inches of rain fall in a normal year.
On November 14 Cotati normally reaches 66° and falls to 43°. The record high is 83°, in 2010; the record low 20°, in 1916. The most rain on this date, 1.77 in, fell in 1953.
Normals 1991–2020 and records since 1893 at Petaluma Airport, 7 miles southeast. NOAA, through RCC-ACIS.
