The Williamson 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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3.45 inches of rain fell in two days, the most for this week of the year since records began in 1895. The next wettest, 2.46 inches, fell in 1992.
Williamson’s center stands about 610 ft above sea level. Within three miles the land runs from 550 ft to 650 ft, a difference of 100 ft: gently rolling country.
Under the town center the state geologic map shows Shelburn-Patoka Formations undivided (shale, limestone), from the Late Pennsylvanian, 304 to 307 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. Age: Late Pennsylvanian, 304 to 307 million years old. About 16 mi of the line.
Shale, sandstone, limestone. Age: Late Pennsylvanian, 304 to 307 million years old. About 9 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 Williamson reaches the Gulf of America by way of Silver Creek, the Kaskaskia and the Mississippi: about 1,190 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Williamson; river miles along the main stem, rounded.
Williamson has a hot-summer humid continental climate. Summer afternoons average 89° in July; winter nights fall to about 21° in January. About 42 inches of rain fall in a normal year.
On November 14 Williamson normally reaches 55° and falls to 36°. The record high is 78°, in 1971; the record low 11°, in 1986. The most rain on this date, 2.25 in, fell in 1993.
Normals 1991–2020 and records since 1895 at Hillsboro, 19 miles northeast. NOAA, through RCC-ACIS.
