The Colwell 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.
Sunny
Partly cloudy; warmer
Mostly sunny
Partly cloudy
Partly cloudy
Mostly sunny
Showers likely
73° on Nov. 13, 1999, the hottest reading for this week of the year since 1893. Next is 72° in 1941.
Colwell’s center stands about 1,150 ft above sea level. Within three miles the land runs from 1,030 ft to 1,190 ft, a difference of 160 ft: gently rolling country.
Under the town center the state geologic map shows Cedar Valley Group (limestone, dolostone), from the Middle Devonian to Late Devonian, 374 to 388 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 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone, dolostone. Age: Middle Devonian to Late Devonian, 374 to 388 million years old. About 23 mi of the line.
Sandstone, shale. Age: Early Cretaceous to Late Cretaceous, 94 to 113 million years old. About 0.6 mi of the line.
Dolostone, limestone. Age: Middle Devonian, 384 to 394 million years old. About 0.3 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 Colwell reaches the Gulf of America by way of Beaver Creek, the Little Cedar, the Cedar River, the Iowa and the Mississippi: about 1,670 river miles.
1,410 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Colwell; river miles along the main stem, rounded.
Colwell has a hot-summer humid continental climate. Summer afternoons average 82° in July; winter nights fall to about 9° in January. A normal year brings about 38 inches of snow; with the rain, that comes to about 38 inches of water.
On November 14 Colwell normally reaches 44° and falls to 27°. The record high is 70°, in 1964; the record low −4°, in 1959. The most rain on this date, 2.20 in, fell in 1902.
Normals 1991–2020 and records since 1893 at Charles City, 8 miles south-southwest, 160 ft lower. NOAA, through RCC-ACIS.
