The South Arm 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 cloudy
Mostly sunny
Mostly sunny
Partly cloudy
Chance of showers
Partly cloudy
74° on Nov. 11, 2022, the hottest reading for this week of the year since 1891. Next is 70° in 2012.
South Arm’s center stands about 740 ft above sea level. Within three miles the land runs from 570 ft to 930 ft, a difference of 360 ft: rolling country. The highest named summit within 15 miles is Deadmans Hill, about 1,340 ft, 14 miles southeast.
Under the town center the state geologic map shows Antrim Shale (black-shale), from the Late Devonian, 359 to 384 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 32×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Limestone. Age: Middle Devonian, 384 to 394 million years old. About 18 mi of the line.
Black-shale. Age: Late Devonian, 359 to 384 million years old. About 5 mi of the line.
Shale. Age: Late Devonian, 359 to 384 million years old. About 1 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 South Arm reaches Lake Michigan by way of the Pine River: about 13 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 South Arm; river miles along the main stem, rounded.
South Arm has a warm-summer humid continental climate. Summer afternoons average 76° in July; winter nights fall to about 16° in February. A normal year brings about 100 inches of snow; with the rain, that comes to about 34 inches of water.
On November 14 South Arm normally reaches 45° and falls to 34°. The record high is 63°, in 1999; the record low 9°, in 1911. The most rain on this date, 1.95 in, fell in 1927.
Normals 1991–2020 and records since 1891 at Charlevoix, 12 miles north-northwest, 150 ft lower. NOAA, through RCC-ACIS.
