The St. Clair 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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74° on Nov. 14, 1999, the hottest reading for this week of the year since 1914. Next is 74° in 2012.
St. Clair’s center stands about 980 ft above sea level. Within three miles the land runs from 970 ft to 1,030 ft, a difference of 60 ft: gently rolling country. The highest named summit within 15 miles is Klondike Hill, about 1,180 ft, 12 miles northeast.
Under the town center the state geologic map shows Lower Ordovician (dolostone, sandstone), 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 58×. 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, sandstone. Age: Early Ordovician, 471 to 487 million years old. About 17 mi of the line.
Sandstone, siltstone, shale. Age: Cambrian, 487 to 497 million years old. About 5 mi of the line.
Shale, limestone, sandstone. Age: Middle Ordovician to Late Ordovician, 445 to 471 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. Clair reaches the Gulf of America by way of the Le Sueur, the Blue Earth, the Minnesota and the Mississippi: about 1,970 river miles.
Lake on the way: Lake Pepin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of St. Clair; river miles along the main stem, rounded.
St. Clair has a warm-summer humid continental climate. Summer afternoons average 81° in July; winter nights fall to about 5° in January. A normal year brings about 52 inches of snow; with the rain, that comes to about 38 inches of water.
On November 14 St. Clair normally reaches 42° and falls to 25°. The record high is 74°, in 1999; the record low −9°, in 1959. The most rain on this date, 0.79 in, fell in 1951.
Normals 1991–2020 and records since 1914 at Waseca Southern Research And Outreach Center, 17 miles east, 170 ft higher. NOAA, through RCC-ACIS.
