The Letts 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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6° on Nov. 13, 2019, the coldest reading for this week of the year since 1938. Next is 8° in 1959.
Letts’s center stands about 890 ft above sea level. Within three miles the land runs from 770 ft to 910 ft, a difference of 140 ft: gently rolling country.
Under the town center the state geologic map shows Louisville Limestone through Brassfield Limestone, from the Silurian, 422 to 445 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 48×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone, dolostone. Age: Devonian, 359 to 422 million years old. About 11 mi of the line.
Limestone. Age: Silurian, 422 to 445 million years old. About 11 mi of the line.
Limestone, shale. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Black-shale. Age: Devonian to Carboniferous, 324 to 422 million years old. About 0.2 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 Letts reaches the Gulf of America by way of Wyaloosing Creek, Sand Creek, the East Fork White, the White River, Big Bayou, the Wabash River Old Channel, the Old Channel Wabash, the Ohio and the Mississippi: about 1,430 river miles.
970 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Letts; river miles along the main stem, rounded.
Letts has a hot-summer humid continental climate. Summer afternoons average 86° in July; winter nights fall to about 23° in January. A normal year brings about 17 inches of snow; with the rain, that comes to about 49 inches of water.
On November 14 Letts normally reaches 56° and falls to 36°. The record high is 75°, in 1971; the record low 10°, in 1986. The most rain on this date, 1.80 in, fell in 1957.
Normals 1991–2020 and records since 1938 at North Vernon 2 ESE, 16 miles south, 170 ft lower. NOAA, through RCC-ACIS.
