The San Luis 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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30° on Nov. 17, 1958, the coldest reading for this week of the year since 1876. Next is 33° in 1964.
San Luis’s center stands about 150 ft above sea level. Within three miles the land runs from 90 ft to 170 ft, a difference of 80 ft: gently rolling country.
Under the town center the state geologic map shows Quaternary surficial deposits, undivided (sand, silt, clay), from the Pleistocene to Holocene, less than 2 million years old.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sand, silt, clay. Age: Pleistocene to Holocene, less than 2 million years old. About 16 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 San Luis reaches the Gulf of California by way of the Colorado: about 90 river miles.
Seldom reaches the sea. Dams and canals now take nearly all of the Colorado before its old delta in Mexico.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of San Luis; river miles along the main stem, rounded.
San Luis has a hot desert climate. Summer afternoons average 107° in July; winter nights fall to about 47° in December. About 3 inches of rain fall in a normal year.
On November 14 San Luis normally reaches 78° and falls to 55°. The record high is 93°, in 1906; the record low 37°, in 1929. The most rain on this date, 0.50 in, fell in 1899.
Normals 1991–2020 and records since 1876 from the Yuma Area threaded record (Yuma International Airport, 14 miles north-northeast). NOAA, through RCC-ACIS.
