The Derry 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
Partly cloudy; warmer
Partly cloudy
Sunny
Sunny
Mostly sunny
Mostly sunny
12° on Nov. 13, 1981, the coldest reading for this week of the year since 1938. Next is 16° in 1986.
Derry’s center stands about 610 ft above sea level. Within three miles the land runs from 500 ft to 1,870 ft, a difference of 1,370 ft: steep hill country. The highest named summit within 15 miles is Thickhead Mountain, about 2,420 ft, 11 miles northwest.
Under the town center the state geologic map shows Wills Creek Formation (shale), from the Silurian, 422 to 445 million years old.
The section below crosses 13 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.
Shale. Age: Silurian, 422 to 445 million years old. About 5 mi of the line.
Shale, sandstone. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Quartzite. Age: Silurian, 422 to 445 million years old. About 3 mi of the line.
Sandstone, shale. Age: Ordovician, 445 to 487 million years old. About 3 mi of the line.
Shale. Age: Ordovician, 445 to 487 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. 7 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 Derry reaches Chesapeake Bay and the Atlantic Ocean by way of Kishacoquillas Creek, the Juniata and the Susquehanna: about 140 river miles.
Lake on the way: Lake Aldred.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Derry; river miles along the main stem, rounded.
Derry has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 21° in January. A normal year brings about 26 inches of snow; with the rain, that comes to about 42 inches of water.
On November 14 Derry normally reaches 53° and falls to 33°. The record high is 75°, in 1989; the record low 17°, in 1986. The most rain on this date, 0.72 in, fell in 1972.
Normals 1991–2020 and records since 1938 at Lewistown, 4 miles south-southwest, 150 ft lower. NOAA, through RCC-ACIS.
