The Colchester 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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71° on Nov. 16, 2001, the hottest reading for this week of the year since 1996. Next is 71° in 2020.
Colchester’s center stands about 470 ft above sea level. Within three miles the land runs from 280 ft to 660 ft, a difference of 380 ft: rolling country. The highest named summit within 15 miles is John Tom Hill, about 930 ft, 12 miles northwest.
Under the town center the state geologic map shows Brimfield Schist (Includes Hamilton Resevoir Formation) (schist, gneiss), from the Cambrian to Ordovician, 445 to 542 million years old.
The section below crosses 10 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 25×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Schist, gneiss. Age: Cambrian to Ordovician, 445 to 542 million years old. About 9 mi of the line.
Schist, calc-silicate-rock. Age: Neoproterozoic, 542 to 1,000 million years old. About 7 mi of the line.
Schist. Age: Silurian to Devonian, 359 to 445 million years old. About 2 mi of the line.
Gneiss. Age: Middle Ordovician, 459 to 471 million years old. About 2 mi of the line.
Gneiss, schist. Age: Neoproterozoic, 542 to 1,000 million years old. About 1 mi of the line.
Gneiss, amphibolite. Age: Early Ordovician to Middle Ordovician, 459 to 487 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. 4 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 Colchester reaches Long Island Sound and the Atlantic Ocean by way of Nelkin Brook, the Jeremy, the Salmon and the Connecticut: about 35 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Colchester; river miles along the main stem, rounded.
Colchester has a hot-summer humid continental climate. Summer afternoons average 83° in July; winter nights fall to about 18° in January. About 43 inches of rain fall in a normal year.
On November 14 Colchester normally reaches 52° and falls to 32°. The record high is 68°, in 2016; the record low 14°, in 2019. The most rain on this date, 0.76 in, fell in 2009.
Normals 1991–2020 and records since 1996 at Willimantic Windham Airport, 14 miles northeast, 220 ft lower. NOAA, through RCC-ACIS.
