The Chinook 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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79° on Nov. 13, 1999, the hottest reading for this week of the year since 1895. Next is 74° in 1990.
Chinook’s center stands about 2,420 ft above sea level. Within three miles the land runs from 2,390 ft to 2,550 ft, a difference of 160 ft: gently rolling country. The highest named summit within 15 miles is Sayer Butte, about 3,720 ft, 14 miles south-southwest.
Under the town center the state geologic map shows Alluvium (gravel, sand, silt), from the Pleistocene to Holocene, less than 1.8 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 20×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale. Age: Late Cretaceous, 72 to 84 million years old. About 11 mi of the line.
Sandstone, shale. Age: Late Cretaceous, 72 to 84 million years old. About 10 mi of the line.
Gravel, sand, silt. Age: Pleistocene to Holocene, less than 1.8 million years old. About 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 Chinook reaches the Gulf of America by way of the Milk River, the Missouri and the Mississippi: about 3,310 river miles.
Lakes on the way: Lake Oahe, Lake Sakakawea, Lake Sharpe and Lake Francis Case.
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 Chinook; river miles along the main stem, rounded.
Chinook has a cold semi-arid climate. Summer afternoons average 84° in July; winter nights fall to about 4° in January. About 13 inches of rain fall in a normal year.
On November 14 Chinook normally reaches 42° and falls to 17°. The record high is 67°, in 1975; the record low −23°, in 1959. The most rain on this date, 0.54 in, fell in 1988.
Normals 1991–2020 and records since 1895 at Chinook, here. NOAA, through RCC-ACIS.
