The Westmont 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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94° on Nov. 12, 1974, the hottest reading for this week of the year since 1944. Next is 93° in 2019.
Westmont’s center stands about 220 ft above sea level. Within three miles the land runs from 50 ft to 240 ft, a difference of 190 ft: gently rolling country. The highest named summit within 15 miles is Cahuenga Peak, about 1,760 ft, 14 miles north.
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 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 34×. 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, less than 2.6 million years old. About 11 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 7 mi of the line.
Sandstone, mudstone. Age: Miocene to Pleistocene, less than 23 million years old. About 2 mi of the line.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 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.
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 Westmont reaches the Pacific Ocean by way of Compton Creek and the Los Angeles: about 10 river miles.
Often dry. About 80% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Westmont; river miles along the main stem, rounded.
Westmont has a cold semi-arid climate. Summer afternoons average 77° in August; winter nights fall to about 49° in December. About 12 inches of rain fall in a normal year.
On November 14 Westmont normally reaches 71° and falls to 54°. The record high is 90°, in 2013; the record low 43°, in 2000. The most rain on this date, 1.27 in, fell in 1972.
Normals 1991–2020 and records since 1944 from the Los Angeles Airport Area threaded record (Los Angeles International Airport, 5 miles west, 120 ft lower). NOAA, through RCC-ACIS.
