The Boyes Hot Springs 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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84° on Nov. 15, 2005, the hottest reading for this week of the year since 1893. Next is 82° in 1906.
Boyes Hot Springs’s center stands about 120 ft above sea level. Within three miles the land runs from 60 ft to 1,390 ft, a difference of 1,330 ft: steep hill country. The highest named summit within 15 miles is Mount Hood, about 2,720 ft, 11 miles north-northwest.
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 7 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.
Dacite. Age: Late Miocene to Late Pliocene, 3 to 7 million years old. About 6 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 6 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 4 mi of the line.
Sandstone, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 4 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 3 mi of the line.
Mica-schist. Age: Early Cretaceous, 110 to 143 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. 1 smaller unit 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 Boyes Hot Springs reaches San Francisco Bay and the Pacific Ocean by way of Sonoma Creek: about 17 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Boyes Hot Springs; river miles along the main stem, rounded.
Boyes Hot Springs has a warm-summer Mediterranean climate. Summer afternoons average 86° in July; winter nights fall to about 38° in January. About 28 inches of rain fall in a normal year.
On November 14 Boyes Hot Springs normally reaches 66° and falls to 42°. The record high is 82°, in 2010; the record low 22°, in 1985. The most rain on this date, 2.05 in, fell in 1953.
Normals 1991–2020 and records since 1893 at Sonoma, here. NOAA, through RCC-ACIS.
