The Portsmouth 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
Mostly sunny; warmer
Partly cloudy
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74° on Nov. 11, 2020, the hottest reading for this week of the year since 1973. Next is 74° in 2022.
Portsmouth’s center stands about 30 ft above sea level. Within three miles the land runs from 0 ft to 120 ft, a difference of 120 ft: gently rolling country. Open water lies within three miles. The highest named summit within 15 miles is Mount Agamenticus, about 690 ft, 11 miles north-northeast.
Under the town center the state geologic map shows Merrimack Group, Kittery Formation (metasandstone, phyllite), from the Ordovician to Silurian, 422 to 487 million years old.
The section below crosses 6 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.
Schist, gneiss, quartzite. Age: Neoproterozoic to Ordovician, 445 to 1,000 million years old. About 5 mi of the line.
Metasandstone, phyllite. Age: Neoproterozoic to Silurian, 422 to 1,000 million years old. About 5 mi of the line.
Granite. Age: Devonian, 359 to 422 million years old. About 4 mi of the line.
Phyllite, quartzite. Age: Neoproterozoic to Silurian, 422 to 1,000 million years old. About 3 mi of the line.
Metasandstone, phyllite. Age: Ordovician to Silurian, 422 to 487 million years old. About 2 mi of the line.
Gneiss. Age: Neoproterozoic to Ordovician, 445 to 1,000 million years old. About 0.3 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 Portsmouth reaches the Atlantic Ocean by way of Sagamore Creek: about 3 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Portsmouth; river miles along the main stem, rounded.
Portsmouth has a warm-summer humid continental climate. Summer afternoons average 81° in July; winter nights fall to about 16° in January. A normal year brings about 65 inches of snow; with the rain, that comes to about 51 inches of water.
On November 14 Portsmouth normally reaches 49° and falls to 32°. The record high is 71°, in 1989; the record low 10°, in 1986. The most rain on this date, 1.90 in, fell in 2006.
Normals 1991–2020 and records since 1973 at Greenland, 5 miles southwest. NOAA, through RCC-ACIS.
