The Brookmont 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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Sunny
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83° on Nov. 15, 1993, the hottest reading for this week of the year since 1871. Next is 80° in 1879.
Brookmont’s center stands about 120 ft above sea level. Within three miles the land runs from 10 ft to 410 ft, a difference of 400 ft: rolling country. The highest named summit within 15 miles is Hunting Hill, about 520 ft, 11 miles north-northwest.
Under the town center the state geologic map shows Wissahickon Formation; Boulder Gneiss (muscovite-gneiss), from the Proterozoic, 542 to 2,500 million years old.
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 39×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Muscovite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 9 mi of the line.
Sand. Age: Cretaceous, 66 to 145 million years old. About 4 mi of the line.
Fine-detrital, coarse-detrital. Age: Quaternary, less than 2.6 million years old. About 3 mi of the line.
Biotite-gneiss. Age: Middle Ordovician to Late Ordovician, 456 to 464 million years old. About 2 mi of the line.
Melange. Age: Cambrian, 487 to 542 million years old. About 2 mi of the line.
Muscovite-gneiss. Age: Proterozoic, 542 to 2,500 million years old. About 1 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 Brookmont reaches Chesapeake Bay and the Atlantic Ocean by way of the Potomac: about 120 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Brookmont; river miles along the main stem, rounded.
Brookmont has a humid subtropical climate. Summer afternoons average 90° in July; winter nights fall to about 30° in January. A normal year brings about 14 inches of snow; with the rain, that comes to about 42 inches of water.
On November 14 Brookmont normally reaches 59° and falls to 42°. The record high is 77°, in 1985; the record low 19°, in 1920. The most rain on this date, 1.56 in, fell in 1972.
Normals 1991–2020 and records since 1871 from the Washington Area threaded record (Washington Reagan National Airport, 8 miles southeast, 110 ft lower). NOAA, through RCC-ACIS.
