The Mattawa 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. 12, 1999, the hottest reading for this week of the year since 1956. Next is 69° in 1976.
Mattawa’s center stands about 760 ft above sea level. Within three miles the land runs from 490 ft to 1,260 ft, a difference of 770 ft: hilly country. The highest named summit within 15 miles is Hog Ranch Buttes, about 4,170 ft, 11 miles west-southwest.
Under the town center the state geologic map shows Younger glacial drift (fine-detrital, coarse-detrital), from the Pleistocene, less than 2.6 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 6×. 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. Age: Late Oligocene to Early Pliocene, 3.6 to 28 million years old. About 9 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 5 mi of the line.
Basalt. Age: Early Eocene to Pliocene, 2.6 to 56 million years old. About 5 mi of the line.
Conglomerate, volcanic. Age: Middle Miocene to Pliocene, 2.6 to 16 million years old. About 2 mi of the line.
Sandstone, clay, volcanic. Age: Pleistocene, less than 2.6 million years old. About 1 mi of the line.
Silt, sand. Age: Holocene, less than 12,000 years old. About 1 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit 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 Mattawa reaches the Pacific Ocean by way of the Columbia: about 400 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 Mattawa; river miles along the main stem, rounded.
Mattawa has a cold semi-arid climate. Summer afternoons average 92° in July; winter nights fall to about 30° in January. About 8 inches of rain fall in a normal year.
On November 14 Mattawa normally reaches 50° and falls to 36°. The record high is 69°, in 2001; the record low 16°, in 2000. The most rain on this date, 0.59 in, fell in 1981.
Normals 1991–2020 and records since 1956 at Priest Rapids Dam, 6 miles south, 330 ft lower. NOAA, through RCC-ACIS.
