The Clearlake 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’s center stands about 1,360 ft above sea level. Within three miles the land runs from 1,320 ft to 2,100 ft, a difference of 780 ft: hilly country. The highest named summit within 15 miles is Cobb Mountain, about 4,730 ft, 12 miles south-southwest.
Under the town center the state geologic map shows Plio-Pleistocene and Pliocene loosely consolidated deposits (sandstone, conglomerate), from the Miocene to Pleistocene, less than 23 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.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 6 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 5 mi of the line.
Andesite. Age: Early Pliocene to Pleistocene, 1.5 to 4 million years old. About 4 mi of the line.
Sandstone, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Greenstone. Age: Jurassic to Cretaceous, 66 to 202 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.
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.
A raindrop that lands in Clearlake reaches San Francisco Bay and the Pacific Ocean by way of the Burns Valley, Cache Creek, Prospect Slough, Cache Slough and the Sacramento: about 140 river miles.
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; river miles along the main stem, rounded.
Clearlake 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 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, 4 miles southeast. NOAA, through RCC-ACIS.
