The Santa Rosa 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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3.48 inches of rain fell in two days, the most for this week of the year since records began in 1902. The next wettest, 3.20 inches, fell in 1920.
Santa Rosa’s center stands about 180 ft above sea level. Within three miles the land runs from 100 ft to 710 ft, a difference of 610 ft: hilly country. The highest named summit within 15 miles is Mount Hood, about 2,720 ft, 9 miles east.
Under the town center the state geologic map shows Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 9×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Dacite. Age: Late Miocene to Late Pliocene, 3 to 7 million years old. About 9 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 8 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 6 mi of the line.
Sandstone, conglomerate. 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.
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 Santa Rosa reaches the Pacific Ocean by way of Santa Rosa Creek, the Laguna de Santa Rosa, Mark West Creek and the Russian: about 35 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Santa Rosa; river miles along the main stem, rounded.
Santa Rosa has a warm-summer Mediterranean climate. Summer afternoons average 84° in September; winter nights fall to about 38° in January. About 32 inches of rain fall in a normal year.
On November 14 Santa Rosa normally reaches 68° and falls to 42°. The record high is 88°, in 2008; the record low 22°, in 1916. The most rain on this date, 2.27 in, fell in 1953.
Normals 1991–2020 and records since 1902 at Santa Rosa, here. NOAA, through RCC-ACIS.
