The Thermal 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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96° on Nov. 12, 1999, the hottest reading for this week of the year since 1950. Next is 95° in 1995.
Thermal’s center stands about 120 ft below sea level. Within three miles the land runs from -160 ft to 90 ft, a difference of 250 ft: rolling country. The highest named summit within 15 miles is Martinez Mountain, about 6,500 ft, 13 miles west-southwest.
Under the town center the state geologic map shows Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 4×. 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 to Holocene, less than 2.6 million years old. About 13 mi of the line.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 3 mi of the line.
Plutonic, gneiss. Age: Paleoproterozoic to Late Cretaceous, 66 to 2,500 million years old. About 3 mi of the line.
Tonalite. Age: Middle Jurassic to Late Cretaceous, 66 to 175 million years old. About 0.2 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Thermal reaches Salton Sea by way of the Whitewater: about 8 river miles. Salton Sea has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Thermal; river miles along the main stem, rounded.
Thermal has a hot desert climate. Summer afternoons average 107° in July; winter nights fall to about 38° in December. About 3 inches of rain fall in a normal year.
On November 14 Thermal normally reaches 79° and falls to 45°. The record high is 93°, in 2008; the record low 25°, in 1994. The most rain on this date, 0.24 in, fell in 1993.
Normals 1991–2020 and records since 1950 at Desert Resorts Regional Airport, here. NOAA, through RCC-ACIS.
