The Lyman 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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−1° on Nov. 17, 2019, the coldest reading for this week of the year since 1894. Next is 0° in 1916.
Lyman’s center stands about 1,230 ft above sea level. Within three miles the land runs from 590 ft to 2,090 ft, a difference of 1,500 ft: steep hill country. The highest named summit within 15 miles is South Peak Kinsman Mountain, about 4,340 ft, 14 miles southeast.
Under the town center the state geologic map shows Ammonoosuc Volcanics of Billings (1935) - metarhyolite tuff, lapilli tuff, tuff breccia, and lava, from the Middle Ordovician to Late Ordovician, 445 to 471 million years old.
The section below crosses 24 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 10×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granodiorite. Age: Early Devonian, 394 to 422 million years old. About 3 mi of the line.
Phyllite, limestone. Age: Silurian to Early Devonian, 394 to 425 million years old. About 3 mi of the line.
Quartzite. Age: Early Devonian, 394 to 422 million years old. About 2 mi of the line.
Metasandstone, metasiltstone, phyllite. Age: Middle Cambrian to Early Ordovician, 485 to 500 million years old. About 2 mi of the line.
Metagraywacke. Age: Early Devonian, 410 to 414 million years old. About 2 mi of the line.
Metarhyolite. Age: Middle Ordovician to Late Ordovician, 445 to 471 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. 18 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 Lyman reaches Long Island Sound and the Atlantic Ocean by way of Patten Brook, Ogontz Brook, the Ammonoosuc and the Connecticut: about 290 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Lyman; river miles along the main stem, rounded.
Lyman 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 Lyman 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, 12 miles north-northwest, 530 ft lower. NOAA, through RCC-ACIS.
