The Sylvan Grove 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. 17, 2016, the hottest reading for this week of the year since 1964. Next is 80° in 2021.
Sylvan Grove’s center stands about 1,460 ft above sea level. Within three miles the land runs from 1,410 ft to 1,660 ft, a difference of 250 ft: rolling country.
Under the town center the state geologic map shows Dakota Formation (claystone, mudstone, shale), from the Early Cretaceous, 100 to 145 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 50×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Claystone, mudstone, shale. Age: Early Cretaceous, 100 to 145 million years old. About 10 mi of the line.
Sand, silt, clay. Age: Pleistocene to Holocene, less than 2.6 million years old. About 8 mi of the line.
Limestone, shale. Age: Late Cretaceous, 66 to 100 million years old. About 4 mi of the line.
Shale, chalk. Age: Late Cretaceous, 66 to 100 million years old. About 0.4 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 Sylvan Grove reaches the Gulf of America by way of the Saline, the Smoky Hill, the Kansas, the Missouri and the Mississippi: about 1,920 river miles.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Sylvan Grove; river miles along the main stem, rounded.
Sylvan Grove has a hot-summer humid continental climate. Summer afternoons average 92° in July; winter nights fall to about 18° in January. A normal year brings about 10 inches of snow; with the rain, that comes to about 26 inches of water.
On November 14 Sylvan Grove normally reaches 57° and falls to 31°. The record high is 78°, in 2025; the record low 4°, in 1986. The most rain on this date, 0.15 in, fell in 1978.
Normals 1991–2020 and records since 1964 at Wilson Lake, 6 miles west-southwest. NOAA, through RCC-ACIS.
