The Thornburg 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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Partly cloudy; warmer
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−2° on Nov. 17, 1959, the coldest reading for this week of the year since 1896. Next is −2° in 2019.
Thornburg’s center stands about 880 ft above sea level. Within three miles the land runs from 780 ft to 890 ft, a difference of 110 ft: gently rolling country.
Under the town center the state geologic map shows Lower Cherokee Group and Raccoon Creek Group (shale, sandstone, siltstone), from the Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old.
The section below crosses 4 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.
Dolostone, limestone. Age: Early Mississippian to Middle Mississippian, 331 to 359 million years old. About 9 mi of the line.
Dolostone, limestone. Age: Middle Mississippian to Late Mississippian, 324 to 347 million years old. About 9 mi of the line.
Shale, sandstone, siltstone. Age: Early Pennsylvanian to Middle Pennsylvanian, 307 to 324 million years old. About 5 mi of the line.
Dolostone, limestone, siltstone. Age: Early Mississippian, 347 to 359 million years old. About 1 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 Thornburg reaches the Gulf of America by way of Smith Creek, Rock Creek, Cedar Creek, the North Skunk, the Skunk and the Mississippi: about 1,500 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Thornburg; river miles along the main stem, rounded.
Thornburg has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 12° in January. About 37 inches of rain fall in a normal year.
On November 14 Thornburg normally reaches 49° and falls to 28°. The record high is 77°, in 1999; the record low 2°, in 1959. The most rain on this date, 1.00 in, fell in 1902.
Normals 1991–2020 and records since 1896 at Sigourney, 10 miles south-southeast, 150 ft lower. NOAA, through RCC-ACIS.
