The De Smet 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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70° on Nov. 11, 1999, the hottest reading for this week of the year since 1915. Next is 69° in 2016.
De Smet’s center stands about 2,630 ft above sea level. Within three miles the land runs from 2,540 ft to 3,710 ft, a difference of 1,170 ft: steep hill country. The highest named summit within 15 miles is Moses Mountain, about 4,950 ft, 6 miles east.
Under the town center the state geologic map shows Sedimentary rocks associated with flood basalts (mixed-clastic), from the Early Miocene to Late Miocene, 8 to 17 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 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.
Mixed-clastic. Age: Early Miocene to Late Miocene, 8 to 17 million years old. About 11 mi of the line.
Silt. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 4 mi of the line.
Metasiltstone, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 3 mi of the line.
Basalt, basaltic-andesite. Age: Early Miocene to Late Miocene, 6 to 18 million years old. About 0.5 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 De Smet reaches the Pacific Ocean by way of Hangman Creek, the Spokane and the Columbia: about 770 river miles.
Lake on the way: Lake Umatilla.
360 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of De Smet; river miles along the main stem, rounded.
De Smet has a dry-summer warm-summer continental climate. Summer afternoons average 84° in August; winter nights fall to about 25° in December. A normal year brings about 41 inches of snow; with the rain, that comes to about 24 inches of water.
On November 14 De Smet normally reaches 45° and falls to 30°. The record high is 60°, in 2025; the record low −12°, in 1955. The most rain on this date, 0.65 in, fell in 1998.
Normals 1991–2020 and records since 1915 at Potlatch 3 NNE, 13 miles south-southeast, 130 ft higher. NOAA, through RCC-ACIS.
