The Rosemont 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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26° on Nov. 17, 1961, the coldest reading for this week of the year since 1856. Next is 27° in 1958.
Rosemont’s center stands about 60 ft above sea level. Within three miles the land runs from 10 ft to 90 ft, a difference of 80 ft: gently rolling country. The highest named summit within 15 miles is Volcano Hill, about 420 ft, 15 miles northeast.
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 2 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 63×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 24 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 0.6 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 Rosemont reaches San Francisco Bay and the Pacific Ocean by way of the Sacramento: about 50 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Rosemont; river miles along the main stem, rounded.
Rosemont has a hot-summer Mediterranean climate. Summer afternoons average 93° in July; winter nights fall to about 38° in December. About 18 inches of rain fall in a normal year.
On November 14 Rosemont normally reaches 66° and falls to 43°. The record high is 81°, in 2010; the record low 27°, in 1978. The most rain on this date, 0.88 in, fell in 1963.
Normals 1991–2020 and records since 1856 from the Sacramento Area threaded record (Sacramento Airport Asos, 8 miles west-southwest). NOAA, through RCC-ACIS.
