The Dedham 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.
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3.71 inches of rain fell in two days, the most for this week of the year since records began in 1893. The next wettest, 3.41 inches, fell in 1947.
Dedham’s center stands about 120 ft above sea level. Within three miles the land runs from 50 ft to 300 ft, a difference of 250 ft: rolling country. The highest named summit within 15 miles is Great Blue Hill, about 630 ft, 3 miles southeast.
Under the town center the state geologic map shows Dedham Granite, from the Neoproterozoic, 615 to 645 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 53×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Conglomerate, sandstone, siltstone. Age: Neoproterozoic to Early Cambrian, 521 to 1,000 million years old. About 4 mi of the line.
Granite. Age: Neoproterozoic, 615 to 645 million years old. About 4 mi of the line.
Rhyolite. Age: Neoproterozoic, 599 to 605 million years old. About 3 mi of the line.
Alkali-granite. Age: Late Ordovician to Silurian, 428 to 459 million years old. About 3 mi of the line.
Granite. Age: Neoproterozoic, 542 to 1,000 million years old. About 2 mi of the line.
Age: Neoproterozoic, 542 to 1,000 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 Dedham reaches Boston Harbor and the Atlantic Ocean by way of the Charles: about 25 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Dedham; river miles along the main stem, rounded.
Dedham has a hot-summer humid continental climate. Summer afternoons average 82° in July; winter nights fall to about 18° in January. A normal year brings about 70 inches of snow; with the rain, that comes to about 54 inches of water.
On November 14 Dedham normally reaches 51° and falls to 34°. The record high is 68°, in 1956; the record low 11°, in 1905. The most rain on this date, 2.08 in, fell in 2009.
Normals 1991–2020 and records since 1893 from the Milton Area threaded record (Blue Hill Lcd, 3 miles southeast, 500 ft higher). NOAA, through RCC-ACIS.
