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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77° on Nov. 12, 1999, the hottest reading for this week of the year since 1881. Next is 69° in 2021.
Lewiston’s center stands about 740 ft above sea level. Within three miles the land runs from 730 ft to 2,550 ft, a difference of 1,820 ft: steep hill country. The highest named summit within 15 miles is Green Knob, about 2,880 ft, 15 miles northeast.
Under the town center the state geologic map shows Alluvial deposits (gravel, sand, silt), from the Quaternary, less than 2.6 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 9×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Basalt, basaltic-andesite. Age: Early Miocene to Late Miocene, 6 to 18 million years old. About 11 mi of the line.
Silt. Age: Pleistocene, less than 2.6 million years old. About 8 mi of the line.
Basalt. Age: Late Oligocene to Early Pliocene, 3.6 to 28 million years old. About 2 mi of the line.
Gravel, sand, silt. Age: Quaternary, less than 2.6 million years old. About 1 mi of the line.
Silt, sand. Age: Holocene, less than 12,000 years old. About 0.6 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene to Holocene, less than 33,000 years old. About 0.3 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 Lewiston reaches the Pacific Ocean by way of the Clearwater, the Snake and the Columbia: about 460 river miles.
Lake on the way: Lake Umatilla.
210 miles of the trip are on the Columbia.
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 cold semi-arid climate. Summer afternoons average 91° in July; winter nights fall to about 30° in January. A normal year brings about 13 inches of snow; with the rain, that comes to about 13 inches of water.
On November 14 Lewiston normally reaches 49° and falls to 35°. The record high is 69°, in 2021; the record low −3°, in 1955. The most rain on this date, 0.84 in, fell in 1988.
Normals 1991–2020 and records since 1881 from the Lewiston Area threaded record (Lewiston Airport, 3 miles south, 690 ft higher). NOAA, through RCC-ACIS.
