The Lewiston 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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71° on Nov. 14, 1999, the hottest reading for this week of the year since 1944. Next is 68° in 2025.
Lewiston’s center stands about 4,510 ft above sea level. Within three miles the land runs from 4,440 ft to 4,560 ft, a difference of 120 ft: gently rolling country. The highest named summit within 15 miles is Naomi Peak, about 9,920 ft, 10 miles east-southeast.
Under the town center the state geologic map shows Lake Bonneville deposits (clay), from the Pleistocene, less than 2.6 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 4×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Clay. Age: Pleistocene, less than 2.6 million years old. About 11 mi of the line.
Mudstone, unconsolidated. Age: Middle Miocene to Late Pliocene, 2.6 to 16 million years old. About 3 mi of the line.
Unconsolidated. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
Limestone. Age: Early Ordovician to Late Ordovician, 445 to 487 million years old. About 1 mi of the line.
Arenite, siltstone-mudstone. Age: Neoproterozoic, 542 to 1,000 million years old. About 1 mi of the line.
Unconsolidated. Age: Pleistocene, less than 2.6 million years old. About 0.9 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 Lewiston reaches Great Salt Lake by way of the Bear River: about 95 river miles. Great Salt Lake has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Lewiston; river miles along the main stem, rounded.
Lewiston has a dry-summer warm-summer continental climate. Summer afternoons average 89° in July; winter nights fall to about 12° in January. A normal year brings about 49 inches of snow; with the rain, that comes to about 17 inches of water.
On November 14 Lewiston normally reaches 48° and falls to 23°. The record high is 71°, in 1999; the record low 1°, in 1978. The most rain on this date, 0.60 in, fell in 1988.
Normals 1991–2020 and records since 1944 at Trenton, 5 miles southwest. NOAA, through RCC-ACIS.
