The Rossmoor 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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95° on Nov. 12, 1974, the hottest reading for this week of the year since 1958. Next is 95° in 2021.
Rossmoor’s center stands about 20 ft above sea level. Within three miles the land runs from 0 ft to 80 ft, a difference of 80 ft: gently rolling country. The highest named summit within 15 miles is San Pedro Hill, about 1,480 ft, 15 miles west-southwest.
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 49×. 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 12 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 3 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 Rossmoor reaches the Pacific Ocean by way of the San Gabriel: about 2 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Rossmoor; river miles along the main stem, rounded.
Rossmoor has a hot semi-arid climate. Summer afternoons average 83° in August; winter nights fall to about 46° in December. About 12 inches of rain fall in a normal year.
On November 14 Rossmoor normally reaches 73° and falls to 52°. The record high is 91°, in 2007; the record low 39°, in 1964. The most rain on this date, 1.07 in, fell in 1972.
Normals 1991–2020 and records since 1958 from the Long Beach Area threaded record (Long Beach Daugherty Airport, 4 miles west-northwest). NOAA, through RCC-ACIS.
