The McKenna 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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5.38 inches of rain fell in two days, the most for this week of the year since records began in 1948. The next wettest, 5.30 inches, fell in 2015.
McKenna’s center stands about 340 ft above sea level. Within three miles the land runs from 280 ft to 500 ft, a difference of 220 ft: rolling country. The highest named summit within 15 miles is Bald Mountain, about 3,630 ft, 15 miles south-southeast.
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 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 10×. 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 16 mi of the line.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 3 mi of the line.
Sandstone. Age: Early Eocene to Middle Eocene, 38 to 56 million years old. About 2 mi of the line.
Andesite, basaltic-andesite. Age: Late Eocene, 34 to 38 million years old. About 2 mi of the line.
Silt, sand. Age: Holocene, less than 12,000 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.
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 McKenna reaches Puget Sound and the Pacific Ocean by way of the Nisqually: about 17 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of McKenna; river miles along the main stem, rounded.
McKenna has a warm-summer Mediterranean climate. Summer afternoons average 78° in July; winter nights fall to about 32° in February. About 51 inches of rain fall in a normal year, with about 4 inches of snow.
On November 14 McKenna normally reaches 51° and falls to 36°. The record high is 65°, in 1995; the record low 3°, in 1955. The most rain on this date, 3.64 in, fell in 2001.
Normals 1991–2020 and records since 1948 from the Olympia Area threaded record (Olympia Airport, 17 miles west, 140 ft lower). NOAA, through RCC-ACIS.
