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.
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5° on Nov. 16, 1933, the coldest reading for this week of the year since 1912. Next is 6° in 2019.
Portsmouth’s center stands about 600 ft above sea level. Within three miles the land runs from 580 ft to 620 ft, a difference of 40 ft: nearly flat ground.
Under the town center the state geologic map shows Saginaw Formation (sandstone, shale), from the Carboniferous, 299 to 324 million years old.
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.
Sandstone, shale. Age: Carboniferous, 299 to 324 million years old. About 20 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 Lake Huron by way of Cheboyganing Creek and the Saginaw: about 12 river miles. From there it moves on through the Great Lakes, over Niagara Falls and down the St. Lawrence to the Atlantic.
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 82° in July; winter nights fall to about 16° in January. A normal year brings about 49 inches of snow; with the rain, that comes to about 32 inches of water.
On November 14 Portsmouth normally reaches 47° and falls to 32°. The record high is 65°, in 2009; the record low 11°, in 1933. The most rain on this date, 1.04 in, fell in 1957.
Normals 1991–2020 and records since 1912 from the Saginaw Area threaded record (Saginaw Mbs International Airport, 13 miles west). NOAA, through RCC-ACIS.
