The St. Helens 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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69° on Nov. 13, 1999, the hottest reading for this week of the year since 1856. Next is 68° in 1899.
St. Helens’s center stands about 90 ft above sea level. Within three miles the land runs from 0 ft to 620 ft, a difference of 620 ft: hilly country. The highest named summit within 15 miles is Davis Peak, about 2,910 ft, 14 miles northeast.
Under the town center the state geologic map shows Columbia River Basalt Group and related flows, from the Miocene, 5.3 to 23 million years old.
The section below crosses 6 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.
Basalt. Age: Miocene, 5.3 to 23 million years old. About 9 mi of the line.
Conglomerate. Age: Pliocene, 2.6 to 5.3 million years old. About 5 mi of the line.
Silt, sand. Age: Holocene, less than 12,000 years old. About 4 mi of the line.
Silt, sand, gravel. Age: Pleistocene, less than 2.6 million years old. About 3 mi of the line.
Basalt, basaltic-andesite. Age: Late Eocene to Oligocene, 23 to 38 million years old. About 2 mi of the line.
Sandstone, siltstone. Age: Late Eocene to Early Miocene, 16 to 38 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.
A raindrop that lands in St. Helens reaches the Pacific Ocean by way of Milton Creek, the Multnomah Channel and the Columbia: about 85 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of St. Helens; river miles along the main stem, rounded.
St. Helens has a warm-summer Mediterranean climate. Summer afternoons average 79° in August; winter nights fall to about 32° in January. About 42 inches of rain fall in a normal year.
On November 14 St. Helens normally reaches 52° and falls to 36°. The record high is 68°, in 1899; the record low 15°, in 1978. The most rain on this date, 2.33 in, fell in 1966.
Normals 1991–2020 and records since 1856 at Vancouver 4 NNE, 15 miles south-southeast, 130 ft higher. NOAA, through RCC-ACIS.
