The Columbia 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.
Columbia’s center stands about 520 ft above sea level. Within three miles the land runs from 260 ft to 750 ft, a difference of 490 ft: hilly country. The highest named summit within 15 miles is Paulk Hill, about 1,000 ft, 13 miles north-northwest.
Under the town center the state geologic map shows Yantic Member [of Tatnic Hill Formation] (schist), from the Neoproterozoic, 542 to 1,000 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 30×. 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, calc-silicate-rock. Age: Neoproterozoic, 542 to 1,000 million years old. About 5 mi of the line.
Schist. Age: Silurian to Devonian, 359 to 445 million years old. About 4 mi of the line.
Gneiss, schist. Age: Neoproterozoic, 542 to 1,000 million years old. About 4 mi of the line.
Gneiss. Age: Middle Ordovician, 459 to 471 million years old. About 3 mi of the line.
Schist, gneiss. Age: Cambrian to Ordovician, 445 to 542 million years old. About 2 mi of the line.
Schist. Age: Neoproterozoic, 542 to 1,000 million years old. About 2 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 Columbia reaches Long Island Sound and the Atlantic Ocean by way of Giffords Brook, the Shetucket and the Thames: about 45 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Columbia; river miles along the main stem, rounded.
Columbia 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 Columbia 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, 7 miles east-northeast, 270 ft lower. NOAA, through RCC-ACIS.
