The Holcomb 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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3.20 inches of rain fell in two days, the most for this week of the year since records began in 1893. The next wettest, 2.72 inches, fell in 1951.
Holcomb’s center stands about 850 ft above sea level. Within three miles the land runs from 750 ft to 890 ft, a difference of 140 ft: gently rolling country.
Under the town center the state geologic map shows Galena Group (Trenton Limestone) (dolostone, limestone), from the Late Ordovician, 447 to 459 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 64×. 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 9 mi of the line.
Dolostone, limestone. Age: Late Ordovician, 454 to 459 million years old. About 9 mi of the line.
Sandstone, limestone, dolostone. Age: Middle Ordovician to Late Ordovician, 454 to 468 million years old. About 6 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 Holcomb reaches the Gulf of America by way of Killbuck Creek, the Rock River and the Mississippi: about 1,600 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Holcomb; river miles along the main stem, rounded.
Holcomb has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 15° in January. A normal year brings about 37 inches of snow; with the rain, that comes to about 37 inches of water.
On November 14 Holcomb normally reaches 48° and falls to 31°. The record high is 73°, in 1971; the record low 4°, in 1959. The most rain on this date, 1.19 in, fell in 1926.
Normals 1991–2020 and records since 1893 from the Rockford Area threaded record (Rockford Greater Rockford Airport, 9 miles north, 120 ft lower). NOAA, through RCC-ACIS.
