The Somerville 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; warmer
Partly cloudy
Mostly sunny
Mostly sunny
Mostly sunny
Partly cloudy
71° on Nov. 11, 2020, the hottest reading for this week of the year since 1948. Next is 71° in 2022.
Somerville’s center stands about 230 ft above sea level. Within three miles the land runs from 180 ft to 570 ft, a difference of 390 ft: rolling country. The highest named summit within 15 miles is Hogback Mountain, about 1,150 ft, 15 miles northeast.
Under the town center the state geologic map shows Ordovician - Precambrian Z Cushing Formation (felsic-volcanic, mafic-volcanic), from the Neoproterozoic to Ordovician, 445 to 1,000 million years old.
The section below crosses 9 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 27×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Slate. Age: Neoproterozoic to Ordovician, 445 to 1,000 million years old. About 6 mi of the line.
Felsic-volcanic, mafic-volcanic. Age: Neoproterozoic to Ordovician, 445 to 1,000 million years old. About 6 mi of the line.
Sandstone. Age: Late Ordovician to Silurian, 428 to 459 million years old. About 4 mi of the line.
Granite. Age: Devonian, 359 to 422 million years old. About 3 mi of the line.
Metasedimentary, metavolcanic. Age: Neoproterozoic to Ordovician, 445 to 1,000 million years old. About 2 mi of the line.
Metavolcanic. Age: Neoproterozoic to Ordovician, 445 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. 3 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 Somerville reaches the Atlantic Ocean by way of Black Brook, Travel Brook and the Sheepscot: about 45 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Somerville; river miles along the main stem, rounded.
Somerville has a warm-summer humid continental climate. Summer afternoons average 80° in July; winter nights fall to about 12° in January. About 42 inches of rain fall in a normal year.
On November 14 Somerville normally reaches 46° and falls to 31°. The record high is 63°, in 2011; the record low 10°, in 2019. The most rain on this date, 2.41 in, fell in 2009.
Normals 1991–2020 and records since 1948 at Augusta State Airport, 15 miles west, 120 ft higher. NOAA, through RCC-ACIS.
