The County Center 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 1960. Next is 80° in 1985.
County Center’s center stands about 360 ft above sea level. Within three miles the land runs from 110 ft to 390 ft, a difference of 280 ft: rolling country.
Under the town center the state geologic map shows Occoquan Granite, from the Cambrian to Ordovician, 445 to 542 million years old.
The section below crosses 12 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 53×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Granite. Age: Cambrian to Ordovician, 445 to 542 million years old. About 5 mi of the line.
Sand. Age: Cretaceous, 66 to 145 million years old. About 4 mi of the line.
Sandstone. Age: Triassic, 202 to 252 million years old. About 3 mi of the line.
Shale, siltstone. Age: Triassic, 202 to 252 million years old. About 2 mi of the line.
Metasiltstone. Age: Cambrian to Ordovician, 445 to 542 million years old. About 2 mi of the line.
Melange. Age: Cambrian, 487 to 542 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. 6 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 County Center reaches Chesapeake Bay and the Atlantic Ocean by way of Airport Creek, the Occoquan and the Potomac: about 100 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of County Center; river miles along the main stem, rounded.
County Center has a humid subtropical climate. Summer afternoons average 88° in July; winter nights fall to about 25° in January. A normal year brings about 21 inches of snow; with the rain, that comes to about 43 inches of water.
On November 14 County Center normally reaches 57° and falls to 36°. The record high is 80°, in 1985; the record low 13°, in 1986. The most rain on this date, 1.90 in, fell in 1972.
Normals 1991–2020 and records since 1960 from the Sterling-Dulles Airport Area threaded record (Washington Dulles International Airport, 17 miles north-northwest). NOAA, through RCC-ACIS.
