The Decatur 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
Mostly sunny; warmer
Mostly sunny
Mostly sunny
Partly cloudy
Partly cloudy
Chance of showers
−7° on Nov. 15, 1959, the coldest reading for this week of the year since 1897. Next is −1° in 2019.
Decatur’s center stands about 820 ft above sea level. Within three miles the land runs from 770 ft to 950 ft, a difference of 180 ft: gently rolling country. The highest named summit within 15 miles is Liberty Pole Hill, about 1,110 ft, 13 miles north.
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 59×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone. Age: Ordovician, 445 to 487 million years old. About 14 mi of the line.
Dolostone. Age: Ordovician, 445 to 487 million years old. About 5 mi of the line.
Dolostone. Age: Early Ordovician, 471 to 487 million years old. About 5 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 Decatur reaches the Gulf of America by way of Sylvester Creek, the Sugar, the Pecatonica, the Rock River and the Mississippi: about 1,650 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Decatur; river miles along the main stem, rounded.
Decatur has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 11° in January. A normal year brings about 37 inches of snow; with the rain, that comes to about 38 inches of water.
On November 14 Decatur normally reaches 47° and falls to 28°. The record high is 71°, in 1999; the record low 3°, in 1986. The most rain on this date, 1.25 in, fell in 1899.
Normals 1991–2020 and records since 1897 at Brodhead Wwtp, here. NOAA, through RCC-ACIS.
