The Steilacoom 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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4.65 inches of rain fell in two days, the most for this week of the year since records began in 1982. The next wettest, 3.43 inches, fell in 2015.
Steilacoom’s center stands about 230 ft above sea level. Within three miles the land runs from 10 ft to 460 ft, a difference of 450 ft: hilly country. Open water lies within three miles. The highest named summit within 15 miles is Black Hill, about 580 ft, 7 miles south-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 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 36×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 10 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 3 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 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.
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.
Rain that falls on Steilacoom runs straight into Puget Sound and the Pacific Ocean.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Steilacoom; river miles along the main stem, rounded.
Steilacoom has a warm-summer Mediterranean climate. Summer afternoons average 77° in July; winter nights fall to about 37° in February. About 41 inches of rain fall in a normal year.
On November 14 Steilacoom normally reaches 53° and falls to 41°. The record high is 65°, in 2021; the record low 24°, in 2014. The most rain on this date, 4.20 in, fell in 2001.
Normals 1991–2020 and records since 1982 at Tacoma No. 1, 10 miles east-northeast, 200 ft lower. NOAA, through RCC-ACIS.
