The Willow Grove 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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81° on Nov. 15, 1993, the hottest reading for this week of the year since 1945. Next is 77° in 2006.
Willow Grove’s center stands about 310 ft above sea level. Within three miles the land runs from 130 ft to 400 ft, a difference of 270 ft: rolling country. The highest named summit within 15 miles is Buckingham Mountain, about 570 ft, 12 miles north-northeast.
The section below crosses 10 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 40×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Arkose. Age: Triassic, 202 to 252 million years old. About 5 mi of the line.
Mica-schist. Age: Paleozoic, 252 to 542 million years old. About 5 mi of the line.
Argillite. Age: Triassic, 202 to 252 million years old. About 4 mi of the line.
Gneiss. Age: Precambrian. About 2 mi of the line.
Mudstone. Age: Triassic, 202 to 252 million years old. About 2 mi of the line.
Sand, clay. Age: Late Cretaceous, 94 to 100 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. 4 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 Willow Grove reaches Delaware Bay and the Atlantic Ocean by way of Pennypack Creek and the Delaware: about 95 river miles.
75 miles of the trip are on the Delaware.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Willow Grove; river miles along the main stem, rounded.
Willow Grove has a humid subtropical climate. Summer afternoons average 88° in July; winter nights fall to about 27° in January. About 45 inches of rain fall in a normal year.
On November 14 Willow Grove normally reaches 57° and falls to 39°. The record high is 74°, in 1993; the record low 20°, in 1986. The most rain on this date, 2.30 in, fell in 1972.
Normals 1991–2020 and records since 1945 at Northeast Philadelphia Airport, 7 miles southeast, 200 ft lower. NOAA, through RCC-ACIS.
