The Idylwood 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.
Partly cloudy
Partly cloudy
Sunny
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Mostly sunny
Mostly sunny
76° on Nov. 12, 2014, the hottest reading for this week of the year since 1925. Next is 75° in 2020.
Idylwood’s center stands about 470 ft above sea level. Within three miles the land runs from 270 ft to 490 ft, a difference of 220 ft: rolling country.
Under the town center the state geologic map shows Mather Gorge Formation - Schist, from the Neoproterozoic to Cambrian, 487 to 1,000 million years old.
The section below crosses 14 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 38×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Schist. Age: Neoproterozoic to Cambrian, 487 to 1,000 million years old. About 7 mi of the line.
Sand. Age: Cretaceous, 66 to 145 million years old. About 3 mi of the line.
Melange. Age: Cambrian, 487 to 542 million years old. About 3 mi of the line.
Gravel, sand. Age: Tertiary, 2.6 to 66 million years old. About 2 mi of the line.
Basalt. Age: Early Jurassic, 175 to 202 million years old. About 1 mi of the line.
Melange. Age: Cambrian, 487 to 542 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. 8 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 Idylwood reaches Chesapeake Bay and the Atlantic Ocean by way of Tripps Run, Holmes Run, Cameron Run and the Potomac: about 120 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Idylwood; river miles along the main stem, rounded.
Idylwood has a humid subtropical climate. Summer afternoons average 84° in July; winter nights fall to about 23° in January. A normal year brings about 18 inches of snow; with the rain, that comes to about 44 inches of water.
On November 14 Idylwood normally reaches 56° and falls to 35°. The record high is 65°, in 2005; the record low 22°, in 2019. The most rain on this date, 1.53 in, fell in 1972.
Normals 1991–2020 and records since 1925 at Vienna, 4 miles west. NOAA, through RCC-ACIS.
