The Harrisburg 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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4.52 inches of rain fell in two days, the most for this week of the year since records began in 1892. The next wettest, 4.46 inches, fell in 1950.
Harrisburg’s center stands about 310 ft above sea level. Within three miles the land runs from 280 ft to 330 ft, a difference of 50 ft: nearly flat ground. The highest named summit within 15 miles is Buck Mountain, about 3,160 ft, 10 miles east-southeast.
Under the town center the state geologic map shows Lacustrine and fluvial sedimentary rocks (clay, silt, sand), 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 7×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 10 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 6 mi of the line.
Basalt, basaltic-andesite. Age: Oligocene to Miocene, 5.3 to 34 million years old. About 2 mi of the line.
Mudstone. Age: Middle Eocene to Late Eocene, 34 to 48 million years old. About 2 mi of the line.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 2 mi of the line.
Sandstone, siltstone. Age: Late Eocene to Oligocene, 23 to 38 million 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 Harrisburg reaches the Pacific Ocean by way of Lake Creek, the Willamette and the Columbia: about 250 river miles.
Lake on the way: Willamette Falls Hydroelectric Power Reservoir.
100 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Harrisburg; river miles along the main stem, rounded.
Harrisburg has a warm-summer Mediterranean climate. Summer afternoons average 84° in July; winter nights fall to about 34° in December. About 41 inches of rain fall in a normal year.
On November 14 Harrisburg normally reaches 54° and falls to 38°. The record high is 68°, in 1912; the record low 14°, in 1978. The most rain on this date, 1.70 in, fell in 1941.
Normals 1991–2020 and records since 1892 from the Eugene Area threaded record (Eugene-Mahlon Sweet Field, 10 miles south-southwest). NOAA, through RCC-ACIS.
