The Alton 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
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73° on Nov. 11, 2020, the hottest reading for this week of the year since 1926. Next is 70° in 2022.
Alton’s center stands about 570 ft above sea level. Within three miles the land runs from 500 ft to 1,370 ft, a difference of 870 ft: hilly country. The highest named summit within 15 miles is Belknap Mountain, about 2,380 ft, 9 miles west-northwest.
Under the town center the state geologic map shows Lower part of Rangeley Formation (metaclastic), from the Silurian, 434 to 445 million years old.
The section below crosses 8 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 12×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Pelitic-schist, metasandstone. Age: Silurian, 434 to 445 million years old. About 7 mi of the line.
Monzodiorite. Age: Jurassic, 145 to 202 million years old. About 5 mi of the line.
Quartzite, metasedimentary. Age: Silurian, 422 to 445 million years old. About 5 mi of the line.
Metaclastic. Age: Silurian, 434 to 445 million years old. About 4 mi of the line.
Granite. Age: Late Devonian, 359 to 384 million years old. About 1 mi of the line.
Granodiorite. Age: Early Devonian, 394 to 422 million years old. About 0.9 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 2 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 Alton reaches the Atlantic Ocean by way of Lake Winnipesaukee, the Winnipesaukee and the Merrimack: about 160 river miles.
Lake on the way: Lake Winnipesaukee.
120 miles of the trip are on the Merrimack.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Alton; river miles along the main stem, rounded.
Alton has a warm-summer humid continental climate. Summer afternoons average 82° in July; winter nights fall to about 12° in January. A normal year brings about 62 inches of snow; with the rain, that comes to about 46 inches of water.
On November 14 Alton normally reaches 48° and falls to 30°. The record high is 62°, in 2010; the record low 8°, in 2019. The most rain on this date, 3.40 in, fell in 1937.
Normals 1991–2020 and records since 1926 at Lakeport 2, 14 miles west-northwest. NOAA, through RCC-ACIS.
