The Hermosa 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.
Partly cloudy
Mostly sunny; warmer
Mostly sunny
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Mostly sunny; cooler
Partly cloudy
Chance of showers
78° on Nov. 12, 1990, the hottest reading for this week of the year since 1942. Next is 78° in 1999.
Hermosa’s center stands about 3,310 ft above sea level. Within three miles the land runs from 3,220 ft to 3,740 ft, a difference of 520 ft: hilly country. The highest named summit within 15 miles is Mount Rushmore, about 5,650 ft, 14 miles west-northwest.
Under the town center the state geologic map shows Alluvium (coarse-detrital, fine-detrital), from the Quaternary, less than 2.6 million years old.
The section below crosses 17 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 10×. 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, fine-detrital. Age: Quaternary, less than 2.6 million years old. About 5 mi of the line.
Claystone, siltstone, sandstone. Age: Eocene to Oligocene, 23 to 56 million years old. About 4 mi of the line.
Shale, bentonite. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Sandstone, siltstone, shale. Age: Late Pennsylvanian to Permian, 273 to 307 million years old. About 2 mi of the line.
Mica-schist, quartzite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 1 mi of the line.
Claystone, conglomerate, sandstone. Age: Early Cretaceous, 100 to 145 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. 11 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 Hermosa reaches the Gulf of America by way of Billover Creek, Battle Creek, the Cheyenne, the Missouri and the Mississippi: about 2,510 river miles.
Lakes on the way: Lake Oahe, Lake Sharpe, Lake Francis Case and Lewis and Clark Lake.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Hermosa; river miles along the main stem, rounded.
Hermosa has a dry-winter hot-summer continental climate. Summer afternoons average 86° in July; winter nights fall to about 13° in January. A normal year brings about 48 inches of snow; with the rain, that comes to about 17 inches of water.
On November 14 Hermosa normally reaches 48° and falls to 22°. The record high is 78°, in 1990; the record low −19°, in 1959. The most rain on this date, 0.52 in, fell in 1956.
Normals 1991–2020 and records since 1942 from the Rapid City Area threaded record (Rapid City Regional Airport, 16 miles north-northeast, 150 ft lower). NOAA, through RCC-ACIS.
