The Mount Wilson 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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−17° on Nov. 13, 2000, the coldest reading for this week of the year since 1974. Next is −10° in 1985.
Mount Wilson’s center stands about 6,600 ft above sea level. Within three miles the land runs from 6,130 ft to 8,600 ft, a difference of 2,470 ft: mountain country. The highest named summit within 15 miles is Mount Wilson, about 9,310 ft, 3 miles east-northeast.
Under the town center the state geologic map shows Intermediate silicic ash flow tuff (felsic-volcanic), from the Oligocene to Early Miocene, 16 to 34 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 6×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Felsic-volcanic. Age: Oligocene to Early Miocene, 16 to 34 million years old. About 13 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 9 mi of the line.
Rhyolite, hypabyssal-rhyolite. Age: Oligocene to Early Miocene, 16 to 34 million years old. About 1 mi of the line.
Shale, siltstone, sandstone. Age: Early Mississippian to Middle Pennsylvanian, 307 to 359 million years old. About 0.3 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 Mount Wilson reaches the Gulf of California by way of Patterson Wash, Meadow Valley Wash, the Muddy and the Colorado: about 650 river miles.
Lakes on the way: Lake Mead, Lake Mohave and Lake Havasu.
290 miles of the trip are on the Colorado.
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 Mount Wilson; river miles along the main stem, rounded.
Mount Wilson has a warm-summer humid continental climate. Summer afternoons average 89° in July; winter nights fall to about 9° in December. About 13 inches of rain fall in a normal year.
On November 14 Mount Wilson normally reaches 54° and falls to 16°. The record high is 73°, in 1999; the record low −10°, in 1985. The most rain on this date, 0.38 in, fell in 1976.
Normals 1991–2020 and records since 1974 at Spring Valley State Park, 20 miles southeast, 650 ft lower. NOAA, through RCC-ACIS.
