The Garnavillo 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.
Sunny
Mostly sunny; warmer
Partly cloudy
Mostly sunny
Partly cloudy
Mostly sunny
Chance of showers
77° on Nov. 13, 1999, the hottest reading for this week of the year since 1937. Next is 72° in 1964.
Garnavillo’s center stands about 1,060 ft above sea level. Within three miles the land runs from 800 ft to 1,090 ft, a difference of 290 ft: rolling country.
Under the town center the state geologic map shows Maquoketa formation (shale, dolostone), from the Late Ordovician, 447 to 454 million years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 37×. 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, limestone. Age: Late Ordovician, 447 to 459 million years old. About 14 mi of the line.
Shale, dolostone. Age: Late Ordovician, 447 to 454 million years old. About 5 mi of the line.
Dolostone. Age: Late Ordovician to Silurian, 434 to 447 million years old. About 2 mi of the line.
Dolostone. Age: Early Ordovician, 471 to 487 million years old. About 1 mi of the line.
Sandstone. Age: Cambrian, 487 to 542 million years old. About 0.8 mi of the line.
Dolostone, sandstone. Age: Early Ordovician to Late Ordovician, 454 to 487 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 Garnavillo reaches the Gulf of America by way of South Cedar Creek, the Turkey and the Mississippi: about 1,610 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Garnavillo; river miles along the main stem, rounded.
Garnavillo has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 10° in January. A normal year brings about 34 inches of snow; with the rain, that comes to about 37 inches of water.
On November 14 Garnavillo normally reaches 47° and falls to 30°. The record high is 71°, in 1990; the record low 4°, in 1959. The most rain on this date, 0.61 in, fell in 1980.
Normals 1991–2020 and records since 1937 at Guttenberg L And D 10, 9 miles southeast, 440 ft lower. NOAA, through RCC-ACIS.
