The Philadelphia 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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79° on Nov. 15, 1993, the hottest reading for this week of the year since 1940. Next is 78° in 2005.
Philadelphia’s center stands about 60 ft above sea level. Within three miles the land runs from 0 ft to 130 ft, a difference of 130 ft: gently rolling country. The highest named summit within 15 miles is Camp Hill, about 360 ft, 12 miles north.
Under the town center the state geologic map shows Trenton Gravel (sand, clay), from the Pleistocene, less than 2.6 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 44×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Mica-schist. Age: Paleozoic, 252 to 542 million years old. About 6 mi of the line.
Sand, clay. Age: Pleistocene, less than 2.6 million years old. About 3 mi of the line.
Granite, gneiss. Age: Paleozoic, 252 to 542 million years old. About 2 mi of the line.
Sand. Age: Late Cretaceous, 84 to 87 million years old. About 2 mi of the line.
Sand, clay. Age: Late Cretaceous, 72 to 84 million years old. About 2 mi of the line.
Gneiss. Age: Precambrian. 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 Philadelphia reaches Delaware Bay and the Atlantic Ocean by way of the Delaware: about 70 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Philadelphia; river miles along the main stem, rounded.
Philadelphia has a humid subtropical climate. Summer afternoons average 89° in July; winter nights fall to about 28° in January. A normal year brings about 16 inches of snow; with the rain, that comes to about 51 inches of water.
On November 14 Philadelphia normally reaches 57° and falls to 42°. The record high is 74°, in 1955; the record low 26°, in 1986. The most rain on this date, 1.09 in, fell in 1940.
Normals 1991–2020 and records since 1940 from the Philadelphia Center City Area threaded record (Philadelphia Franklin Institute, here). NOAA, through RCC-ACIS.
