The Mendon 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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−7° on Nov. 16, 1978, the coldest reading for this week of the year since 1969. Next is −1° in 1985.
Mendon’s center stands about 4,490 ft above sea level. Within three miles the land runs from 4,410 ft to 7,400 ft, a difference of 2,990 ft: mountain country. The highest named summit within 15 miles is Logan Peak, about 9,690 ft, 13 miles east.
Under the town center the state geologic map shows Lake Bonneville deposits (clay), from the Pleistocene, less than 2.6 million years old.
The section below crosses 11 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 4×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Unconsolidated. Age: Quaternary, less than 2.6 million years old. About 9 mi of the line.
Clay. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Sandstone, carbonate. Age: Middle Pennsylvanian to Permian, 273 to 315 million years old. About 4 mi of the line.
Peat. Age: Holocene, less than 12,000 years old. About 1.0 mi of the line.
Mudstone, unconsolidated. Age: Middle Miocene to Late Pliocene, 2.6 to 16 million years old. About 0.7 mi of the line.
Dolostone, shale. Age: Middle Cambrian, 497 to 521 million years old. About 0.7 mi of the line.
From the USGS State Geologic Map Compilation (Horton and others, 2017), the states’ geologic maps joined at a common scale. 5 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 Mendon reaches Great Salt Lake by way of the Bear River: about 80 river miles. Great Salt Lake has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Mendon; river miles along the main stem, rounded.
Mendon has a dry-summer warm-summer continental climate. Summer afternoons average 88° in July; winter nights fall to about 12° in January. A normal year brings about 52 inches of snow; with the rain, that comes to about 18 inches of water.
On November 14 Mendon normally reaches 47° and falls to 25°. The record high is 67°, in 2025; the record low 7°, in 1978. The most rain on this date, 0.77 in, fell in 2006.
Normals 1991–2020 and records since 1969 at Logan 5 SW Experiment Farm, 5 miles southeast. NOAA, through RCC-ACIS.
