The St. Thomas 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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4.57 inches of rain fell in two days, the most for this week of the year since records began in 1894. The next wettest, 3.48 inches, fell in 2009.
St. Thomas’s center stands about 770 ft above sea level. Within three miles the land runs from 520 ft to 790 ft, a difference of 270 ft: rolling country. The highest named summit within 15 miles is High Point, about 960 ft, 14 miles south-southwest.
Under the town center the state geologic map shows Smithville Dolomite, Powell Dolomite, Cotter Dolomite, Jefferson City Dolomite (dolostone), from the Early Ordovician, 471 to 487 million years old.
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 45×. 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. Age: Early Ordovician, 471 to 487 million years old. About 17 mi of the line.
Sandstone, chert. Age: Early Ordovician, 471 to 487 million years old. About 5 mi of the line.
Dolostone. Age: Early Ordovician, 471 to 487 million years old. About 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 St. Thomas reaches the Gulf of America by way of Profits Creek, the Osage, the Missouri and the Mississippi: about 1,330 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of St. Thomas; river miles along the main stem, rounded.
St. Thomas has a hot-summer humid continental climate. Summer afternoons average 89° in July; winter nights fall to about 22° in January. About 40 inches of rain fall in a normal year.
On November 14 St. Thomas normally reaches 57° and falls to 35°. The record high is 81°, in 2025; the record low 4°, in 1986. The most rain on this date, 1.64 in, fell in 1985.
Normals 1991–2020 and records since 1894 from the Jefferson City Area threaded record (Jefferson City Memorial Airport, 16 miles north-northeast, 230 ft lower). NOAA, through RCC-ACIS.
