The Ottawa 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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76° on Nov. 14, 1999, the hottest reading for this week of the year since 1893. Next is 73° in 2012.
Ottawa’s center stands about 810 ft above sea level. Within three miles the land runs from 730 ft to 990 ft, a difference of 260 ft: rolling country.
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 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 52×. 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 11 mi of the line.
Sandstone, siltstone, shale. Age: Cambrian, 487 to 497 million years old. About 9 mi of the line.
Sandstone, siltstone, shale. Age: Middle Cambrian to Cambrian, 487 to 521 million years old. About 2 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 Ottawa reaches the Gulf of America by way of the Minnesota and the Mississippi: about 1,900 river miles.
Lake on the way: Lake Pepin.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Ottawa; river miles along the main stem, rounded.
Ottawa has a warm-summer humid continental climate. Summer afternoons average 82° in July; winter nights fall to about 3° in January. A normal year brings about 38 inches of snow; with the rain, that comes to about 32 inches of water.
On November 14 Ottawa normally reaches 43° and falls to 23°. The record high is 76°, in 1999; the record low −8°, in 1959. The most rain on this date, 1.50 in, fell in 1997.
Normals 1991–2020 and records since 1893 at St. Peter, 4 miles south-southwest. NOAA, through RCC-ACIS.
