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.
Mostly cloudy
Mostly cloudy; warmer
Mostly cloudy
Sunny
Sunny
Mostly sunny
Mostly sunny
79° on Nov. 15, 2011, the hottest reading for this week of the year since 1974. Next is 78° in 2020.
Londonderry’s center stands about 1,000 ft above sea level. Within three miles the land runs from 880 ft to 2,650 ft, a difference of 1,770 ft: steep hill country. The highest named summit within 15 miles is Sampson Rock, about 2,940 ft, 13 miles southwest.
Under the town center the state geologic map shows Foreknobs Formation (sandstone), from the Late Devonian, 359 to 384 million years old.
The section below crosses 17 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 9×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone. Age: Late Devonian, 359 to 384 million years old. About 5 mi of the line.
Quartzite. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Sandstone, siltstone, shale. Age: Late Devonian, 359 to 384 million years old. About 3 mi of the line.
Shale, siltstone, sandstone. Age: Carboniferous, 324 to 359 million years old. About 2 mi of the line.
Shale, sandstone. Age: Silurian, 422 to 445 million years old. About 2 mi of the line.
Limestone. Age: Silurian to Devonian, 359 to 445 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. 11 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 Londonderry reaches Chesapeake Bay and the Atlantic Ocean by way of Wills Creek, the North Branch Potomac and the Potomac: about 330 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 87° in July; winter nights fall to about 23° in January. A normal year brings about 29 inches of snow; with the rain, that comes to about 39 inches of water.
On November 14 Londonderry normally reaches 54° and falls to 34°. The record high is 71°, in 1993; the record low 13°, in 1986. The most rain on this date, 0.72 in, fell in 1997.
Normals 1991–2020 and records since 1974 at Cumberland 2, 13 miles south, 270 ft lower. NOAA, through RCC-ACIS.
