The Grinnell 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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Chance of showers; warmer
81° on Nov. 16, 1941, the hottest reading for this week of the year since 1892. Next is 81° in 1999.
Grinnell’s center stands about 2,910 ft above sea level. Within three miles the land runs from 2,790 ft to 2,950 ft, a difference of 160 ft: gently rolling country.
Under the town center the state geologic map shows Loess (silt), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 2 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 54×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Silt. Age: Pleistocene to Holocene, less than 2.6 million years old. About 22 mi of the line.
Arkose. Age: Miocene, 5.3 to 23 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 Grinnell reaches the Gulf of America by way of North Fork Big Creek, Big Creek, the Smoky Hill, the Kansas, the Missouri and the Mississippi: about 2,150 river miles.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Grinnell; river miles along the main stem, rounded.
Grinnell has a dry-winter hot-summer continental climate. Summer afternoons average 92° in July; winter nights fall to about 16° in January. A normal year brings about 26 inches of snow; with the rain, that comes to about 21 inches of water.
On November 14 Grinnell normally reaches 54° and falls to 26°. The record high is 81°, in 1999; the record low −2°, in 2014. The most rain on this date, 0.53 in, fell in 1926.
Normals 1991–2020 and records since 1892 at Oakley 4 W, 17 miles west, 190 ft higher. NOAA, through RCC-ACIS.
