The Dennis 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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83° on Nov. 16, 2025, the hottest reading for this week of the year since 1923. Next is 82° in 1934.
Dennis’s center stands about 900 ft above sea level. Within three miles the land runs from 740 ft to 950 ft, a difference of 210 ft: rolling country.
Under the town center the state geologic map shows Keokuk and Reeds Spring Formations and St. Joe Group (chert, limestone), from the Carboniferous, 324 to 359 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 41×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Chert, limestone. Age: Carboniferous, 324 to 359 million years old. About 19 mi of the line.
Limestone, shale. Age: Carboniferous, 324 to 359 million years old. About 4 mi of the line.
Shale, sandstone. Age: Carboniferous, 299 to 324 million years old. About 0.7 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 Dennis reaches the Gulf of America by way of the Neosho, the Arkansas and the Mississippi: about 1,100 river miles.
Lakes on the way: Murray Lake and Ozark Lake.
600 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Dennis; river miles along the main stem, rounded.
Dennis has a humid subtropical climate. Summer afternoons average 91° in July; winter nights fall to about 26° in January. A normal year brings about 6 inches of snow; with the rain, that comes to about 47 inches of water.
On November 14 Dennis normally reaches 61° and falls to 39°. The record high is 82°, in 1999; the record low 13°, in 1940. The most rain on this date, 3.15 in, fell in 1985.
Normals 1991–2020 and records since 1923 at Spavinaw, 14 miles southwest, 220 ft lower. NOAA, through RCC-ACIS.
