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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81° on Nov. 11, 2020, the hottest reading for this week of the year since 1948. Next is 80° in 1985.
Philadelphia’s center stands about 880 ft above sea level. Within three miles the land runs from 820 ft to 1,170 ft, a difference of 350 ft: rolling country. The highest named summit within 15 miles is Roy Knob, about 1,570 ft, 11 miles south-southwest.
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 34×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Dolostone, limestone. Age: Ordovician, 445 to 487 million years old. About 8 mi of the line.
Dolostone. Age: Cambrian, 487 to 542 million years old. About 4 mi of the line.
Dolostone. Age: Cambrian, 487 to 542 million years old. About 3 mi of the line.
Shale. Age: Ordovician, 445 to 487 million years old. About 2 mi of the line.
Shale. 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.
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 Philadelphia reaches the Gulf of America by way of Sweetwater Creek, the Tennessee, the Ohio and the Mississippi: about 1,600 river miles.
Lakes on the way: Guntersville Lake, White Lake (historical), Pickwick Lake and Cummings Lake.
970 miles of the trip are on the Mississippi.
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. About 55 inches of rain fall in a normal year, with about 4 inches of snow.
On November 14 Philadelphia normally reaches 62° and falls to 37°. The record high is 80°, in 1985; the record low 19°, in 2019. The most rain on this date, 0.82 in, fell in 2024.
Normals 1991–2020 and records since 1948 at Lenoir City, 11 miles northeast. NOAA, through RCC-ACIS.
