The Thornbury 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
Mostly sunny; warmer
Partly cloudy
Sunny
Sunny
Mostly sunny
Mostly sunny
79° on Nov. 15, 1993, the hottest reading for this week of the year since 1931. Next is 75° in 1973.
Thornbury’s center stands about 450 ft above sea level. Within three miles the land runs from 180 ft to 490 ft, a difference of 310 ft: rolling country. The highest named summit within 15 miles is Diamond Rock Hill, about 700 ft, 11 miles north.
Under the town center the state geologic map shows Felsic and intermediate gneiss, from the Precambrian.
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 26×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Gneiss. Age: Precambrian. About 5 mi of the line.
Gneiss. Age: Precambrian. About 3 mi of the line.
Mica-schist. Age: Paleozoic, 252 to 542 million years old. About 3 mi of the line.
Granite. Age: Paleozoic, 252 to 542 million years old. About 2 mi of the line.
Age: Paleozoic, 252 to 542 million years old. About 2 mi of the line.
Muscovite-gneiss. Age: Precambrian. 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 Thornbury reaches Delaware Bay and the Atlantic Ocean by way of Chester Creek and the Delaware: about 65 river miles.
50 miles of the trip are on the Delaware.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Thornbury; river miles along the main stem, rounded.
Thornbury has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 24° in January. A normal year brings about 12 inches of snow; with the rain, that comes to about 50 inches of water.
On November 14 Thornbury normally reaches 53° and falls to 37°. The record high is 73°, in 1993; the record low 21°, in 1986. The most rain on this date, 2.17 in, fell in 1972.
Normals 1991–2020 and records since 1931 at Wilmington Porter Res, 10 miles south, 180 ft lower. NOAA, through RCC-ACIS.
