The Harrison 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.
Mostly sunny
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68° on Nov. 12, 1999, the hottest reading for this week of the year since 1897. Next is 63° in 1937.
Harrison’s center stands about 2,190 ft above sea level. Within three miles the land runs from 2,120 ft to 3,130 ft, a difference of 1,010 ft: steep hill country. The highest named summit within 15 miles is Round Top, about 5,440 ft, 14 miles east-southeast.
Under the town center the state geologic map shows Columbia River Basalt Group (basalt, basaltic-andesite), from the Early Miocene to Late Miocene, 6 to 18 million years old.
The section below crosses 3 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 13 mi of the line.
Metasiltstone, quartzite, argillite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 4 mi of the line.
Age: Mesoproterozoic, 1 to 1.6 billion years old. About 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 Harrison reaches the Pacific Ocean by way of Harrison Slough, the Spokane and the Columbia: about 760 river miles.
Lakes on the way: Harrison Slough and Lake Umatilla.
360 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Harrison; river miles along the main stem, rounded.
Harrison has a dry-summer warm-summer continental climate. Summer afternoons average 84° in July; winter nights fall to about 24° in January. A normal year brings about 56 inches of snow; with the rain, that comes to about 31 inches of water.
On November 14 Harrison normally reaches 44° and falls to 30°. The record high is 62°, in 1899; the record low 4°, in 1955. The most rain on this date, 1.50 in, fell in 1897.
Normals 1991–2020 and records since 1897 at Saint Maries, 14 miles southeast. NOAA, through RCC-ACIS.
