The Letha 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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−13° on Nov. 15, 1955, the coldest reading for this week of the year since 1906. Next is −2° in 2014.
Letha’s center stands about 2,280 ft above sea level. Within three miles the land runs from 2,260 ft to 2,750 ft, a difference of 490 ft: hilly country. The highest named summit within 15 miles is Little Butte, about 3,490 ft, 10 miles east-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 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 16×. 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 14 mi of the line.
Gravel, sand, silt. Age: Quaternary, less than 2.6 million years old. About 5 mi of the line.
Gravel, sand, silt. Age: Pliocene to Pleistocene, less than 5.3 million years old. About 2 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene to Holocene, less than 33,000 years old. About 2 mi of the line.
Basalt, basaltic-andesite. Age: Early Miocene to Late Miocene, 6 to 18 million years old. About 2 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 Letha reaches the Pacific Ocean by way of Sevenmile Slough, the Payette, the Snake and the Columbia: about 710 river miles.
Lakes on the way: Lake Umatilla, Brownlee Reservoir and Hells Canyon Reservoir.
240 miles of the trip are on the Snake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Letha; river miles along the main stem, rounded.
Letha has a cold semi-arid climate. Summer afternoons average 92° in July; winter nights fall to about 23° in January. A normal year brings about 7 inches of snow; with the rain, that comes to about 13 inches of water.
On November 14 Letha normally reaches 50° and falls to 29°. The record high is 70°, in 1953; the record low 7°, in 1916. The most rain on this date, 0.77 in, fell in 1965.
Normals 1991–2020 and records since 1906 at Emmett 2 E, 9 miles east-southeast, 110 ft higher. NOAA, through RCC-ACIS.
