The Prosser 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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76° on Nov. 13, 1987, the hottest reading for this week of the year since 1925. Next is 76° in 1999.
Prosser’s center stands about 660 ft above sea level. Within three miles the land runs from 610 ft to 1,820 ft, a difference of 1,210 ft: steep hill country. The highest named summit within 15 miles is Chandler Butte, about 2,030 ft, 10 miles east-northeast.
Under the town center the state geologic map shows Glaciolacustrine deposits (silt, sand), from the Pleistocene, less than 2.6 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 11×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Silt. Age: Pleistocene, less than 2.6 million years old. About 16 mi of the line.
Silt, sand. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Basalt. Age: Late Oligocene to Early Pliocene, 3.6 to 28 million years old. About 1 mi of the line.
Basalt. Age: Early Eocene to Pliocene, 2.6 to 56 million years old. About 0.7 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 Prosser reaches the Pacific Ocean by way of the Yakima and the Columbia: about 380 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 Prosser; river miles along the main stem, rounded.
Prosser has a cold semi-arid climate. Summer afternoons average 90° in July; winter nights fall to about 26° in December. About 9 inches of rain fall in a normal year.
On November 14 Prosser normally reaches 50° and falls to 32°. The record high is 75°, in 1999; the record low 7°, in 1955. The most rain on this date, 0.62 in, fell in 1926.
Normals 1991–2020 and records since 1925 at Prosser, here, 170 ft higher. NOAA, through RCC-ACIS.
