The Longtown 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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5.13 inches of rain fell in two days, the most for this week of the year since records began in 1907. The next wettest, 3.67 inches, fell in 1993.
Longtown’s center stands about 650 ft above sea level. Within three miles the land runs from 510 ft to 650 ft, a difference of 140 ft: gently rolling country.
Under the town center the state geologic map shows Decorah Group, Plattin Group (limestone), from the Middle Ordovician, 459 to 471 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 39×. 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. Age: Middle Ordovician, 459 to 471 million years old. About 9 mi of the line.
Dolostone. Age: Early Ordovician, 471 to 487 million years old. About 5 mi of the line.
Dolostone, limestone, shale. Age: Middle Ordovician, 459 to 471 million years old. About 3 mi of the line.
Dolostone, sandstone, limestone. Age: Early Ordovician to Middle Ordovician, 459 to 487 million years old. About 3 mi of the line.
Limestone, sandstone, shale. Age: Middle Mississippian, 331 to 347 million years old. About 2 mi of the line.
Clay, silt, sand. Age: Holocene, less than 12,000 years old. About 0.9 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 1 smaller unit along the line are not listed.
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 Longtown reaches the Gulf of America by way of Indian Creek, Apple Creek and the Mississippi: about 1,070 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Longtown; river miles along the main stem, rounded.
Longtown has a hot-summer humid continental climate. Summer afternoons average 88° in July; winter nights fall to about 21° in January. About 46 inches of rain fall in a normal year, with about 5 inches of snow.
On November 14 Longtown normally reaches 56° and falls to 33°. The record high is 86°, in 1989; the record low 10°, in 1976. The most rain on this date, 3.20 in, fell in 1993.
Normals 1991–2020 and records since 1907 at Perryville Water Plt, 9 miles west-northwest, 150 ft lower. NOAA, through RCC-ACIS.
