The Cedar Mill 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 1872. Next is 68° in 1976.
Cedar Mill’s center stands about 260 ft above sea level. Within three miles the land runs from 180 ft to 1,130 ft, a difference of 950 ft: steep hill country. The highest named summit within 15 miles is Bald Peak, about 1,650 ft, 15 miles southwest.
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 16×. 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 17 mi of the line.
Sandstone-mudstone. Age: Pliocene to Pleistocene, less than 5.3 million years old. About 2 mi of the line.
Basalt. Age: Miocene, 5.3 to 23 million years old. About 2 mi of the line.
Silt, sand, gravel. Age: Pleistocene, less than 2.6 million years old. About 1 mi of the line.
Sand, gravel, silt. Age: Holocene, less than 12,000 years old. About 0.7 mi of the line.
Basaltic-andesite, basalt. Age: Early Pliocene to Pleistocene, 1.2 to 3.9 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. 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 Cedar Mill reaches the Pacific Ocean by way of Cedar Mill Creek, Beaverton Creek, Rock 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 Cedar Mill; river miles along the main stem, rounded.
Cedar Mill has a warm-summer Mediterranean climate. Summer afternoons average 81° in August; winter nights fall to about 37° in January. About 44 inches of rain fall in a normal year, with about 4 inches of snow.
On November 14 Cedar Mill normally reaches 53° and falls to 42°. The record high is 66°, in 2001; the record low 18°, in 1955. The most rain on this date, 2.18 in, fell in 1876.
Normals 1991–2020 and records since 1872 from the Portland Downtown Area threaded record (Portland Kgw-Tv, 6 miles east, 100 ft lower). NOAA, through RCC-ACIS.
