The Olney 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.
Mostly cloudy
Partly cloudy
Sunny
Sunny
Sunny
Mostly sunny
Mostly sunny
16° on Nov. 16, 1996, the coldest reading for this week of the year since 1993. Next is 18° in 2017.
Olney’s center stands about 540 ft above sea level. Within three miles the land runs from 340 ft to 550 ft, a difference of 210 ft: rolling country.
Under the town center the state geologic map shows Norbeck Quartz Diorite (quartz-diorite), from the Middle Cambrian, 500 to 520 million years old.
The section below crosses 7 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 29×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Biotite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 7 mi of the line.
Muscovite-schist. Age: Proterozoic, 542 to 2,500 million years old. About 6 mi of the line.
Phyllite. Age: Proterozoic, 542 to 2,500 million years old. About 3 mi of the line.
Sand. Age: Cretaceous, 66 to 145 million years old. About 3 mi of the line.
Muscovite-gneiss. Age: Proterozoic, 542 to 2,500 million years old. About 3 mi of the line.
Quartz-diorite. Age: Middle Cambrian, 500 to 520 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. 1 smaller unit 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 Olney reaches Chesapeake Bay and the Atlantic Ocean by way of Williamsburg Run, Rock Creek and the Potomac: about 140 river miles.
110 miles of the trip are on the Potomac.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Olney; river miles along the main stem, rounded.
Olney has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 25° in January. A normal year brings about 31 inches of snow; with the rain, that comes to about 48 inches of water.
On November 14 Olney normally reaches 54° and falls to 37°. The record high is 74°, in 1993; the record low 22°, in 2019. The most rain on this date, 1.90 in, fell in 1995.
Normals 1991–2020 and records since 1993 at Damascus 3 SSW, 12 miles northwest, 160 ft higher. NOAA, through RCC-ACIS.
