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.
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12° on Nov. 13, 2019, the coldest reading for this week of the year since 1976. Next is 16° in 1986.
Somerville’s center stands about 400 ft above sea level. Within three miles the land runs from 330 ft to 500 ft, a difference of 170 ft: gently rolling country.
Under the town center the state geologic map shows Loess (silt), from the Quaternary, less than 2.6 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 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Silt. Age: Quaternary, less than 2.6 million years old. About 12 mi of the line.
Sand. Age: Tertiary, 2.6 to 66 million years old. About 10 mi of the line.
Fine-detrital, coarse-detrital. Age: Quaternary, less than 2.6 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.
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 Gulf of America by way of Town Branch, the Loosahatchie and the Mississippi: about 820 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 humid subtropical climate. Summer afternoons average 91° in July; winter nights fall to about 30° in January. About 58 inches of rain fall in a normal year.
On November 14 Somerville normally reaches 63° and falls to 40°. The record high is 79°, in 1999; the record low 12°, in 2019. The most rain on this date, 1.86 in, fell in 2024.
Normals 1991–2020 and records since 1976 at Ames Plantation, 12 miles southeast, 140 ft higher. NOAA, through RCC-ACIS.
