The Nampa 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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−3° on Nov. 15, 1955, the coldest reading for this week of the year since 1875. Next is 1° in 2014.
Nampa’s center stands about 2,520 ft above sea level. Within three miles the land runs from 2,470 ft to 2,600 ft, a difference of 130 ft: gently rolling country. The highest named summit within 15 miles is Kuna Butte, about 3,220 ft, 9 miles southeast.
Under the town center the state geologic map shows Basalt (Pleistocene and Pliocene), from the Late Pliocene to Pleistocene, less than 3 million years old.
The section below crosses 4 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 26×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Basalt. Age: Late Pliocene to Pleistocene, less than 3 million years old. About 16 mi of the line.
Coarse-detrital, fine-detrital. Age: Pleistocene to Holocene, less than 33,000 years old. About 6 mi of the line.
Gravel, sand, silt. Age: Pliocene to Pleistocene, less than 5.3 million years old. About 2 mi of the line.
Gravel, sand, silt. Age: Quaternary, less than 2.6 million years old. About 0.6 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 Nampa reaches the Pacific Ocean by way of Indian Creek, the Boise, the Snake and the Columbia: about 740 river miles.
Lakes on the way: Lake Umatilla, Brownlee Reservoir and Hells Canyon Reservoir.
240 miles of the trip are on the Snake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Nampa; river miles along the main stem, rounded.
Nampa has a cold semi-arid climate. Summer afternoons average 93° in July; winter nights fall to about 25° in January. A normal year brings about 18 inches of snow; with the rain, that comes to about 12 inches of water.
On November 14 Nampa normally reaches 49° and falls to 32°. The record high is 72°, in 1934; the record low 1°, in 1955. The most rain on this date, 0.52 in, fell in 1965.
Normals 1991–2020 and records since 1875 from the Boise Area threaded record (Boise Air Terminal, 16 miles east, 300 ft higher). NOAA, through RCC-ACIS.
