The Bon Homme Colony 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.
Partly cloudy
Mostly sunny; warmer
Mostly sunny
Partly cloudy
Partly cloudy
Partly cloudy; cooler
Showers likely
83° on Nov. 15, 2025, the hottest reading for this week of the year since 1893. Next is 81° in 1953.
Bon Homme Colony’s center stands about 1,270 ft above sea level. Within three miles the land runs from 1,200 ft to 1,570 ft, a difference of 370 ft: rolling country.
Under the town center the state geologic map shows Niobrara Formation (chalk, marlstone, shale), from the Late Cretaceous, 66 to 100 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 33×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Chalk, marlstone, shale. Age: Late Cretaceous, 66 to 100 million years old. About 9 mi of the line.
Siltstone-mudstone, conglomerate-sandstone. Age: Miocene, 5.3 to 23 million years old. About 6 mi of the line.
Shale. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Shale. Age: Late Cretaceous, 66 to 100 million years old. About 3 mi of the line.
Limestone, shale. Age: Late Cretaceous, 66 to 100 million years old. About 2 mi of the line.
Shale, bentonite. Age: Late Cretaceous, 66 to 100 million years old. About 0.6 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 Bon Homme Colony reaches the Gulf of America by way of Lewis and Clark Lake, the Missouri and the Mississippi: about 1,980 river miles.
Lake on the way: Lewis and Clark Lake.
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 Bon Homme Colony; river miles along the main stem, rounded.
Bon Homme Colony has a hot-summer humid continental climate. Summer afternoons average 86° in July; winter nights fall to about 9° in January. A normal year brings about 37 inches of snow; with the rain, that comes to about 26 inches of water.
On November 14 Bon Homme Colony normally reaches 46° and falls to 24°. The record high is 77°, in 1999; the record low −19°, in 1959. The most rain on this date, 0.84 in, fell in 1926.
Normals 1991–2020 and records since 1893 at Tyndall, 12 miles northwest, 150 ft higher. NOAA, through RCC-ACIS.
