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.
Sunny
Partly cloudy; warmer
Mostly sunny
Mostly sunny
Partly cloudy
Mostly sunny
Showers likely
78° on Nov. 11, 2012, the hottest reading for this week of the year since 1893. Next is 74° in 1931.
Chelsea’s center stands about 790 ft above sea level. Within three miles the land runs from 770 ft to 980 ft, a difference of 210 ft: 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 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, limestone, dolostone. Age: Late Devonian, 374 to 384 million years old. About 18 mi of the line.
Limestone, dolostone. Age: Middle Devonian to Late Devonian, 374 to 388 million years old. About 7 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 Otter Creek, the Iowa and the Mississippi: about 1,570 river miles.
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 84° in July; winter nights fall to about 10° in January. A normal year brings about 28 inches of snow; with the rain, that comes to about 36 inches of water.
On November 14 Chelsea normally reaches 48° and falls to 28°. The record high is 73°, in 1999; the record low −2°, in 1916. The most rain on this date, 1.80 in, fell in 1899.
Normals 1991–2020 and records since 1893 at Belle Plaine, 7 miles east-southeast. NOAA, through RCC-ACIS.
