The Mahopac 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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77° on Nov. 11, 2020, the hottest reading for this week of the year since 1950. Next is 69° in 2022.
Mahopac’s center stands about 780 ft above sea level. Within three miles the land runs from 400 ft to 930 ft, a difference of 530 ft: hilly country. The highest named summit within 15 miles is South Beacon Mountain, about 1,580 ft, 13 miles northwest.
Under the town center the state geologic map shows Biotite granite gneiss (biotite-gneiss), from the Mesoproterozoic, 1 to 1.6 billion 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 19×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Biotite-gneiss. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 8 mi of the line.
Gneiss. Age: Precambrian to Mesoproterozoic. About 5 mi of the line.
Biotite-gneiss. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 3 mi of the line.
Gneiss, quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 2 mi of the line.
Age: Mesoproterozoic, 1 to 1.6 billion years old. About 2 mi of the line.
Gneiss. Age: Precambrian to Mesoproterozoic. 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 Mahopac reaches New York Harbor and the Atlantic Ocean by way of the Muscoot, the Croton and the Hudson: about 60 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Mahopac; river miles along the main stem, rounded.
Mahopac has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 17° in January. About 50 inches of rain fall in a normal year.
On November 14 Mahopac normally reaches 53° and falls to 32°. The record high is 68°, in 1964; the record low 17°, in 2019. The most rain on this date, 1.18 in, fell in 1955.
Normals 1991–2020 and records since 1950 at Shrub Oak, 6 miles west-southwest, 320 ft lower. NOAA, through RCC-ACIS.
