The Rumsey 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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82° on Nov. 12, 2014, the hottest reading for this week of the year since 1954. Next is 81° in 1995.
Rumsey’s center stands about 430 ft above sea level. Within three miles the land runs from 390 ft to 2,680 ft, a difference of 2,290 ft: mountain country. The highest named summit within 15 miles is Brushy Sky High, about 3,170 ft, 14 miles west.
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 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 7×. 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, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 7 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 5 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 5 mi of the line.
Serpentinite. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 5 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous, 113 to 145 million years old. About 2 mi of the line.
Siltstone-mudstone. Age: Late Jurassic to Early Cretaceous, 100 to 164 million years old. About 0.4 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 Rumsey reaches San Francisco Bay and the Pacific Ocean by way of Cache Creek, Prospect Slough, Cache Slough and the Sacramento: about 100 river miles.
80 miles of the trip are on Cache Creek.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Rumsey; river miles along the main stem, rounded.
Rumsey has a hot-summer Mediterranean climate. Summer afternoons average 91° in July; winter nights fall to about 32° in December. About 30 inches of rain fall in a normal year.
On November 14 Rumsey normally reaches 64° and falls to 36°. The record high is 81°, in 1995; the record low 23°, in 1978. The most rain on this date, 3.07 in, fell in 1965.
Normals 1991–2020 and records since 1954 at Clearlake 4 SE, 18 miles west, 920 ft higher. NOAA, through RCC-ACIS.
