The Upper Allen 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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76° on Nov. 15, 1973, the hottest reading for this week of the year since 1888. Next is 76° in 1993.
Upper Allen’s center stands about 560 ft above sea level. Within three miles the land runs from 400 ft to 670 ft, a difference of 270 ft: rolling country. The highest named summit within 15 miles is Long Mountain, about 1,570 ft, 10 miles southwest.
Under the town center the state geologic map shows Hamburg sequence rocks (shale), from the Ordovician, 445 to 487 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 20×. 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: Ordovician, 445 to 487 million years old. About 9 mi of the line.
Dolostone. Age: Cambrian, 487 to 542 million years old. About 4 mi of the line.
Age: Precambrian. About 3 mi of the line.
Quartzite. Age: Cambrian, 487 to 542 million years old. About 2 mi of the line.
Limestone. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Limestone. Age: Ordovician, 445 to 487 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 Upper Allen reaches Chesapeake Bay and the Atlantic Ocean by way of Yellow Breeches Creek and the Susquehanna: about 85 river miles.
Lake on the way: Lake Aldred.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Upper Allen; river miles along the main stem, rounded.
Upper Allen 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 30 inches of snow; with the rain, that comes to about 44 inches of water.
On November 14 Upper Allen normally reaches 54° and falls to 36°. The record high is 74°, in 1989; the record low 19°, in 1986. The most rain on this date, 1.74 in, fell in 1995.
Normals 1991–2020 and records since 1888 from the Middletown-Harrisburg Area threaded record (Middletown Harrisburg Int'L Airport, 11 miles east, 260 ft lower). NOAA, through RCC-ACIS.
