The Day Valley 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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89° on Nov. 15, 2008, the hottest reading for this week of the year since 1937. Next is 89° in 2019.
Day Valley’s center stands about 1,390 ft above sea level. Within three miles the land runs from 340 ft to 2,520 ft, a difference of 2,180 ft: mountain country. The highest named summit within 15 miles is Loma Prieta, about 3,780 ft, 5 miles north.
Under the town center the state geologic map shows Pliocene marine rocks (sandstone, mudstone), from the Miocene to Pleistocene, less than 23 million years old.
The section below crosses 9 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.
Coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 3 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 3 mi of the line.
Sandstone, mudstone. Age: Miocene to Pleistocene, less than 23 million years old. About 2 mi of the line.
Sandstone, siltstone-mudstone. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Mudstone, sandstone. Age: Paleocene to Oligocene, 23 to 66 million years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 3 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 Day Valley reaches the Pacific Ocean by way of Valencia Creek and Aptos Creek: about 5 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Day Valley; river miles along the main stem, rounded.
Day Valley has a warm-summer Mediterranean climate. Summer afternoons average 90° in August; winter nights fall to about 37° in January. About 50 inches of rain fall in a normal year.
On November 14 Day Valley normally reaches 72° and falls to 40°. The record high is 88°, in 2021; the record low 27°, in 1985. The most rain on this date, 3.42 in, fell in 1972.
Normals 1991–2020 and records since 1937 at Ben Lomond No. 4, 13 miles west-northwest, 960 ft lower. NOAA, through RCC-ACIS.
