The Grafton 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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3.52 inches of rain fell in two days, the most for this week of the year since records began in 1940. The next wettest, 3.36 inches, fell in 2009.
Grafton’s center stands about 450 ft above sea level. Within three miles the land runs from 410 ft to 860 ft, a difference of 450 ft: hilly country. The highest named summit within 15 miles is Tucker Knob, about 890 ft, 4 miles west-northwest.
Under the town center the state geologic map shows Silurian System undivided (dolostone, limestone), from the Silurian, 422 to 445 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 39×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone. Age: Early Mississippian to Middle Mississippian, 331 to 359 million years old. About 8 mi of the line.
Clay, silt, sand. Age: Holocene, less than 12,000 years old. About 7 mi of the line.
Limestone, shale. Age: Early Mississippian, 347 to 359 million years old. About 4 mi of the line.
Dolostone, limestone. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Limestone, dolostone. Age: Late Ordovician, 447 to 454 million years old. About 1 mi of the line.
Shale, limestone. Age: Late Ordovician, 445 to 454 million years old. About 1 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 Grafton reaches the Gulf of America by way of the Mississippi: about 1,190 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Grafton; river miles along the main stem, rounded.
Grafton has a hot-summer humid continental climate. Summer afternoons average 87° in July; winter nights fall to about 19° in January. A normal year brings about 12 inches of snow; with the rain, that comes to about 42 inches of water.
On November 14 Grafton normally reaches 53° and falls to 34°. The record high is 80°, in 1999; the record low 8°, in 1940. The most rain on this date, 1.40 in, fell in 1993.
Normals 1991–2020 and records since 1940 at Jerseyville 2 SW, 10 miles north-northeast, 160 ft higher. NOAA, through RCC-ACIS.
