The Groton 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.
Chance of showers
Mostly cloudy
Mostly cloudy
Mostly sunny; warmer
Mostly sunny
Partly cloudy
Partly cloudy
−1° on Nov. 17, 2019, the coldest reading for this week of the year since 1894. Next is 0° in 1916.
Groton’s center stands about 810 ft above sea level. Within three miles the land runs from 750 ft to 1,660 ft, a difference of 910 ft: steep hill country. The highest named summit within 15 miles is Signal Mountain, about 3,360 ft, 6 miles west.
Under the town center the state geologic map shows Waits River Formation - carbonaceous phyllite and limestone member (phyllite, limestone), from the Silurian to Early Devonian, 394 to 425 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 7×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Phyllite, limestone. Age: Silurian to Early Devonian, 394 to 425 million years old. About 11 mi of the line.
Granite. Age: Devonian, 359 to 422 million years old. About 5 mi of the line.
Metasandstone, metasiltstone, phyllite. Age: Middle Cambrian to Early Ordovician, 485 to 500 million years old. About 4 mi of the line.
Quartzite. Age: Early Devonian, 394 to 422 million years old. About 2 mi of the line.
Slate, phyllite. Age: Late Ordovician, 445 to 459 million years old. About 1 mi of the line.
Metasedimentary. Age: Silurian to Early Devonian, 394 to 428 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. 2 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 Groton reaches Long Island Sound and the Atlantic Ocean by way of the Wells and the Connecticut: about 280 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Groton; river miles along the main stem, rounded.
Groton has a warm-summer humid continental climate. Summer afternoons average 81° in July; winter nights fall to about 9° in January. A normal year brings about 87 inches of snow; with the rain, that comes to about 40 inches of water.
On November 14 Groton normally reaches 46° and falls to 29°. The record high is 64°, in 1989; the record low 3°, in 1905. The most rain on this date, 1.64 in, fell in 1937.
Normals 1991–2020 and records since 1894 at Saint Johnsbury, 17 miles north-northeast, 110 ft lower. NOAA, through RCC-ACIS.
