The Londonderry 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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74° on Nov. 11, 2020, the hottest reading for this week of the year since 1885. Next is 74° in 2022.
Londonderry’s center stands about 430 ft above sea level. Within three miles the land runs from 220 ft to 500 ft, a difference of 280 ft: rolling country. The highest named summit within 15 miles is North Mountain, about 1,330 ft, 15 miles northwest.
Under the town center the state geologic map shows Merrimack Group, Berwick Formation, Unnamed member (schist, granofels), from the Ordovician to Silurian, 422 to 487 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 48×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granofels, biotite-schist. Age: Ordovician to Silurian, 422 to 487 million years old. About 10 mi of the line.
Schist, granofels. Age: Ordovician to Silurian, 422 to 487 million years old. About 7 mi of the line.
Granite. Age: Early Devonian to Late Devonian, 359 to 422 million years old. About 4 mi of the line.
Gneiss, biotite-schist, granofels. Age: Neoproterozoic, 542 to 1,000 million years old. About 3 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Londonderry reaches the Atlantic Ocean by way of Watts Brook and the Merrimack: about 65 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Londonderry; river miles along the main stem, rounded.
Londonderry has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 17° in January. About 40 inches of rain fall in a normal year.
On November 14 Londonderry normally reaches 51° and falls to 33°. The record high is 66°, in 2011; the record low 16°, in 2019. The most rain on this date, 1.77 in, fell in 2009.
Normals 1991–2020 and records since 1885 from the Manchester Area threaded record (Manchester Airport, 5 miles northwest, 200 ft lower). NOAA, through RCC-ACIS.
