The Harrison 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.
Chance of showers
Partly cloudy
Chance of showers
Showers likely; cooler
Partly cloudy
Chance of showers
Chance of showers
71° on Nov. 12, 1999, the hottest reading for this week of the year since 1907. Next is 68° in 2016.
Harrison’s center stands about 4,890 ft above sea level. Within three miles the land runs from 4,710 ft to 5,260 ft, a difference of 550 ft: hilly country. The highest named summit within 15 miles is Hollowtop Mountain, about 10,590 ft, 13 miles west-southwest.
Under the town center the state geologic map shows Alluvium (gravel, sand, silt), from the Pleistocene to Holocene, less than 1.8 million years old.
The section below crosses 7 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.
Gravel, sand, silt. Age: Pleistocene to Holocene, less than 1.8 million years old. About 7 mi of the line.
Granitic. Age: Cretaceous, 66 to 145 million years old. About 5 mi of the line.
Siltstone, sedimentary-breccia, conglomerate. Age: Early Eocene to Early Miocene, 16 to 56 million years old. About 4 mi of the line.
Gneiss, amphibolite. Age: Archean. About 3 mi of the line.
Gneiss. Age: Archean. About 3 mi of the line.
Age: Pleistocene to Holocene, less than 1.8 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. 1 smaller unit 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 Harrison reaches the Gulf of America by way of Willow Creek, the Jefferson, the Missouri and the Mississippi: about 3,510 river miles.
Lakes on the way: Lake Oahe, Lake Sakakawea, Lake Fort Peck and Lake Sharpe.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Harrison; river miles along the main stem, rounded.
Harrison has a warm-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 24° 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 Harrison normally reaches 47° and falls to 31°. The record high is 69°, in 1999; the record low −7°, in 1955. The most rain on this date, 0.36 in, fell in 2017.
Normals 1991–2020 and records since 1907 at Norris Madison Power House, 17 miles south-southeast, 140 ft lower. NOAA, through RCC-ACIS.
