The Alta 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 sunny
Partly cloudy; warmer
Mostly sunny
Partly cloudy
Partly cloudy
Mostly sunny
Showers likely
76° on Nov. 11, 2012, the hottest reading for this week of the year since 1893. Next is 74° in 1999.
Alta’s center stands about 1,490 ft above sea level. Within three miles the land runs from 1,390 ft to 1,510 ft, a difference of 120 ft: gently rolling country.
Under the town center the state geologic map shows Dakata and Windrow Formations (sandstone, shale), from the Early Cretaceous to Late Cretaceous, 94 to 113 million years old.
The section below crosses 2 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Sandstone, shale. Age: Early Cretaceous to Late Cretaceous, 94 to 113 million years old. About 23 mi of the line.
Limestone. Age: Early Mississippian to Middle Mississippian, 331 to 359 million years old. About 0.8 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 Alta reaches the Gulf of America by way of the Little Maple, the Maple, the Little Sioux, the Missouri and the Mississippi: about 1,920 river miles.
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 Alta; river miles along the main stem, rounded.
Alta has a hot-summer humid continental climate. Summer afternoons average 82° in July; winter nights fall to about 9° in January. About 34 inches of rain fall in a normal year.
On November 14 Alta normally reaches 45° and falls to 27°. The record high is 70°, in 2001; the record low −9°, in 1940. The most rain on this date, 0.88 in, fell in 1902.
Normals 1991–2020 and records since 1893 at Storm Lake, 5 miles east-southeast. NOAA, through RCC-ACIS.
