The Lake Nacimiento 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. 17, 2008, the hottest reading for this week of the year since 1894. Next is 89° in 2025.
Lake Nacimiento’s center stands about 990 ft above sea level. Within three miles the land runs from 650 ft to 1,790 ft, a difference of 1,140 ft: steep hill country. The highest named summit within 15 miles is Pine Mountain, about 3,610 ft, 12 miles west-southwest.
Under the town center the state geologic map shows Upper Cretaceous and Paleocene marine rocks, undivided (sandstone), from the Late Cretaceous to Paleocene, 56 to 100 million years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 7×. 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. Age: Late Cretaceous to Paleocene, 56 to 100 million years old. About 10 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pleistocene, less than 23 million years old. About 8 mi of the line.
Sandstone, mudstone. Age: Oligocene to Pliocene, 2.6 to 34 million years old. About 3 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 1 mi of the line.
Sandstone, mudstone. Age: Jurassic to Cretaceous, 66 to 202 million years old. About 1 mi of the line.
Hypabyssal-rhyolite. Age: Early Miocene, 16 to 18 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.
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 Lake Nacimiento reaches the Pacific Ocean by way of Snake Creek and the Salinas: about 130 river miles.
Lake on the way: Lake Nacimiento.
110 miles of the trip are on the Salinas.
Often dry. About 80% of the way is mapped as streams that run only after rain or snowmelt; the water makes the whole trip in floods.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Lake Nacimiento; river miles along the main stem, rounded.
Lake Nacimiento has a hot-summer Mediterranean climate. Summer afternoons average 92° in August; winter nights fall to about 32° in December. About 15 inches of rain fall in a normal year.
On November 14 Lake Nacimiento normally reaches 70° and falls to 37°. The record high is 86°, in 2019; the record low 16°, in 1916. The most rain on this date, 2.21 in, fell in 1953.
Normals 1991–2020 and records since 1894 at Paso Robles, 13 miles east-southeast, 260 ft lower. NOAA, through RCC-ACIS.
