The Great Valley 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.
Showers likely
Mostly cloudy
Mostly cloudy
Sunny
Mostly sunny
Partly cloudy
Partly cloudy
74° on Nov. 11, 2020, the hottest reading for this week of the year since 1941. Next is 70° in 1956.
Great Valley’s center stands about 1,460 ft above sea level. Within three miles the land runs from 1,440 ft to 2,210 ft, a difference of 770 ft: hilly country. The highest named summit within 15 miles is Shutts Hill, about 2,460 ft, 10 miles west.
Under the town center the state geologic map shows Conneaut Group, undivided (shale, sandstone), from the Late Devonian, 359 to 384 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 20×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale, sandstone. Age: Late Devonian, 359 to 384 million years old. About 15 mi of the line.
Shale. Age: Late Devonian, 359 to 384 million years old. About 8 mi of the line.
Shale, siltstone, sandstone. Age: Late Devonian, 359 to 384 million years old. About 0.6 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale.
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 Great Valley reaches the Gulf of America by way of Wrights Creek, the Allegheny, the Ohio and the Mississippi: about 2,190 river miles.
Lake on the way: Allegheny Reservoir.
970 miles of the trip are on the Ohio.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Great Valley; river miles along the main stem, rounded.
Great Valley has a warm-summer humid continental climate. Summer afternoons average 79° in July; winter nights fall to about 13° in January. A normal year brings about 133 inches of snow; with the rain, that comes to about 49 inches of water.
On November 14 Great Valley normally reaches 47° and falls to 29°. The record high is 67°, in 2010; the record low 11°, in 1942. The most rain on this date, 1.10 in, fell in 1972.
Normals 1991–2020 and records since 1941 at Little Valley, 9 miles west-northwest, 160 ft higher. NOAA, through RCC-ACIS.
