The Chelsea 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.
Mostly sunny
Sunny; warmer
Mostly sunny
Partly cloudy
Partly cloudy
Partly cloudy; cooler
Showers likely
−17° on Nov. 14, 2014, the coldest reading for this week of the year since 1893. Next is −15° in 1959.
Chelsea’s center stands about 1,340 ft above sea level. Within three miles the land runs from 1,320 ft to 1,370 ft, a difference of 50 ft: nearly flat ground.
Under the town center the state geologic map shows Pierre Shale (shale, bentonite), from the Late Cretaceous, 66 to 100 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 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.
Shale, bentonite. Age: Late Cretaceous, 66 to 100 million years old. About 18 mi of the line.
Chalk, marlstone, shale. Age: Late Cretaceous, 66 to 100 million years old. About 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 Chelsea reaches the Gulf of America by way of Perry Creek, South Fork Snake Creek, Snake Creek, the James, the Missouri and the Mississippi: about 2,310 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 Chelsea; river miles along the main stem, rounded.
Chelsea has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 2° in January. A normal year brings about 43 inches of snow; with the rain, that comes to about 22 inches of water.
On November 14 Chelsea normally reaches 43° and falls to 20°. The record high is 68°, in 2015; the record low −17°, in 2014. The most rain on this date, 1.00 in, fell in 1895.
Normals 1991–2020 and records since 1893 from the Aberdeen Area threaded record (Aberdeen Regional Airport, 25 miles northeast). NOAA, through RCC-ACIS.
