The Griswold 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.
Partly cloudy
Mostly sunny; warmer
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12° on Nov. 16, 1996, the coldest reading for this week of the year since 1956. Next is 14° in 1956.
Griswold’s center stands about 220 ft above sea level. Within three miles the land runs from 140 ft to 530 ft, a difference of 390 ft: rolling country. The highest named summit within 15 miles is Shaw Hill, about 780 ft, 14 miles north-northwest.
Under the town center the state geologic map shows Quinebaug Formation (gneiss), from the Ordovician to Middle Ordovician, 459 to 487 million years old.
The section below crosses 11 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 31×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Gneiss. Age: Neoproterozoic, 542 to 1,000 million years old. About 6 mi of the line.
Gneiss, schist. Age: Neoproterozoic, 542 to 1,000 million years old. About 5 mi of the line.
Gneiss. Age: Ordovician to Middle Ordovician, 459 to 487 million years old. About 5 mi of the line.
Gneiss. Age: Neoproterozoic, 542 to 1,000 million years old. About 3 mi of the line.
Granite. Age: Devonian, 359 to 422 million years old. About 2 mi of the line.
Mylonite, gneiss. Age: Paleozoic, 252 to 542 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. 5 smaller units along the line are not listed.
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 Griswold reaches Long Island Sound and the Atlantic Ocean by way of Crooked Brook, the Pachaug, the Quinebaug, the Shetucket and the Thames: about 30 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Griswold; river miles along the main stem, rounded.
Griswold has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 21° in January. A normal year brings about 28 inches of snow; with the rain, that comes to about 52 inches of water.
On November 14 Griswold normally reaches 54° and falls to 35°. The record high is 72°, in 1993; the record low 17°, in 1986. The most rain on this date, 2.25 in, fell in 1972.
Normals 1991–2020 and records since 1956 at Norwich Public Utility Plant, 8 miles west-southwest, 200 ft lower. NOAA, through RCC-ACIS.
