The Clearlake Riviera 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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82° on Nov. 12, 2014, the hottest reading for this week of the year since 1954. Next is 81° in 1995.
Clearlake Riviera’s center stands about 1,880 ft above sea level. Within three miles the land runs from 1,320 ft to 3,710 ft, a difference of 2,390 ft: mountain country. The highest named summit within 15 miles is Cobb Mountain, about 4,730 ft, 10 miles south.
Under the town center the state geologic map shows Quaternary volcanic flow rocks, unit 3 (Clear Lake Volcanic Field) (andesite), from the Early Pliocene to Pleistocene, 1.5 to 4 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Andesite. Age: Early Pliocene to Pleistocene, 1.5 to 4 million years old. About 12 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 5 mi of the line.
Sandstone, mudstone. Age: Paleocene, 56 to 66 million years old. About 2 mi of the line.
Siltstone-mudstone. Age: Late Jurassic to Early Cretaceous, 100 to 164 million years old. About 2 mi of the line.
Siltstone-mudstone. Age: Early Cretaceous, 113 to 145 million years old. About 1 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 0.7 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 2 smaller units along the line are not listed.
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.
Clearlake Riviera straddles the rim of a basin with no outlet. Rain on the southwest side runs to Clear Lake; most of the rest goes to San Francisco Bay and the Pacific Ocean.
From the center of town, a raindrop reaches San Francisco Bay and the Pacific Ocean by way of Clear Lake, Cache Creek, Prospect Slough, Cache Slough and the Sacramento: about 150 river miles. Rain that falls on Clearlake Riviera runs only a short way, about 2 miles, to Clear Lake. Clear Lake has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
Lake on the way: Clear Lake.
120 miles of the trip are on Cache Creek.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Clearlake Riviera; river miles along the main stem, rounded.
Clearlake Riviera has a hot-summer Mediterranean climate. Summer afternoons average 91° in July; winter nights fall to about 32° in December. About 30 inches of rain fall in a normal year.
On November 14 Clearlake Riviera normally reaches 64° and falls to 36°. The record high is 81°, in 1995; the record low 23°, in 1978. The most rain on this date, 3.07 in, fell in 1965.
Normals 1991–2020 and records since 1954 at Clearlake 4 SE, 9 miles east-southeast, 530 ft lower. NOAA, through RCC-ACIS.
