The Forest Grove 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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71° on Nov. 13, 1999, the hottest reading for this week of the year since 1893. Next is 68° in 1962.
Forest Grove’s center stands about 190 ft above sea level. Within three miles the land runs from 150 ft to 630 ft, a difference of 480 ft: hilly country. The highest named summit within 15 miles is South Saddle Mountain, about 3,440 ft, 13 miles west.
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 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.
Clay, silt, sand. Age: Pleistocene, less than 2.6 million years old. About 8 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 5 mi of the line.
Basalt. Age: Middle Eocene to Late Eocene, 34 to 48 million years old. About 4 mi of the line.
Gabbro. Age: Oligocene, 23 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.
Siltstone. Age: Middle Eocene to Late Eocene, 34 to 48 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. 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 Forest Grove reaches the Pacific Ocean by way of Council Creek, Dairy Creek, the Tualatin, the Willamette and the Columbia: about 180 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 Forest Grove; river miles along the main stem, rounded.
Forest Grove has a warm-summer Mediterranean climate. Summer afternoons average 82° in August; winter nights fall to about 33° in January. About 47 inches of rain fall in a normal year, with about 3 inches of snow.
On November 14 Forest Grove normally reaches 51° and falls to 36°. The record high is 67°, in 1996; the record low 12°, in 1955. The most rain on this date, 3.98 in, fell in 1896.
Normals 1991–2020 and records since 1893 at Forest Grove, here. NOAA, through RCC-ACIS.
