The Edgemont 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.
Mostly cloudy
Sunny; warmer
Partly cloudy
Partly cloudy
Mostly sunny; cooler
Partly cloudy
Showers likely
−21° on Nov. 13, 2014, the coldest reading for this week of the year since 1948. Next is −17° in 1986.
Edgemont’s center stands about 3,520 ft above sea level. Within three miles the land runs from 3,410 ft to 3,780 ft, a difference of 370 ft: rolling country. The highest named summit within 15 miles is Parker Peak, about 4,810 ft, 10 miles northeast.
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 17×. 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 11 mi of the line.
Claystone, conglomerate, sandstone. Age: Early Cretaceous, 100 to 145 million years old. About 5 mi of the line.
Shale, mudstone, marlstone. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Sandstone, siltstone, claystone. Age: Middle Jurassic to Late Jurassic, 145 to 175 million years old. About 2 mi of the line.
Coarse-detrital, clay. Age: Quaternary, less than 2.6 million years old. About 2 mi of the line.
Chalk, marlstone, shale. Age: Late Cretaceous, 66 to 100 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. 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 Edgemont reaches the Gulf of America by way of the Cheyenne, the Missouri and the Mississippi: about 2,570 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 Edgemont; river miles along the main stem, rounded.
Edgemont has a cold semi-arid climate. Summer afternoons average 89° in July; winter nights fall to about 4° in January. A normal year brings about 36 inches of snow; with the rain, that comes to about 16 inches of water.
On November 14 Edgemont normally reaches 48° and falls to 15°. The record high is 71°, in 2023; the record low −21°, in 2014. The most rain on this date, 0.22 in, fell in 2013.
Normals 1991–2020 and records since 1948 at Edgemont, here. NOAA, through RCC-ACIS.
