The Bryn Mawr 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 1940. Next is 78° in 2005.
Bryn Mawr’s center stands about 430 ft above sea level. Within three miles the land runs from 190 ft to 470 ft, a difference of 280 ft: rolling country. The highest named summit within 15 miles is Diamond Rock Hill, about 700 ft, 11 miles west-northwest.
Under the town center the state geologic map shows Wissahickon Formation (mica-schist), from the Paleozoic, 252 to 542 million years old.
The section below crosses 17 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.
Mica-schist. Age: Paleozoic, 252 to 542 million years old. About 5 mi of the line.
Sand. Age: Miocene, 5.3 to 23 million years old. About 3 mi of the line.
Schist, phyllite. Age: Paleozoic, 252 to 542 million years old. About 2 mi of the line.
Gneiss. Age: Precambrian. About 2 mi of the line.
Sand, clay. Age: Late Cretaceous, 94 to 100 million years old. About 2 mi of the line.
Limestone. 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. 11 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 Bryn Mawr reaches Delaware Bay and the Atlantic Ocean by way of Mill Creek, the Schuylkill and the Delaware: about 80 river miles.
60 miles of the trip are on the Delaware.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Bryn Mawr; river miles along the main stem, rounded.
Bryn Mawr has a humid subtropical climate. Summer afternoons average 89° in July; winter nights fall to about 28° in January. A normal year brings about 16 inches of snow; with the rain, that comes to about 51 inches of water.
On November 14 Bryn Mawr normally reaches 57° and falls to 42°. The record high is 74°, in 1955; the record low 26°, in 1986. The most rain on this date, 1.09 in, fell in 1940.
Normals 1991–2020 and records since 1940 from the Philadelphia Center City Area threaded record (Philadelphia Franklin Institute, 8 miles east-southeast, 370 ft lower). NOAA, through RCC-ACIS.
