The Ahtanum 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
Showers likely
Chance of showers
Partly cloudy
72° on Nov. 13, 1999, the hottest reading for this week of the year since 1946. Next is 72° in 2021.
Ahtanum’s center stands about 1,230 ft above sea level. Within three miles the land runs from 1,090 ft to 2,220 ft, a difference of 1,130 ft: steep hill country. The highest named summit within 15 miles is Pine Mountain, about 4,290 ft, 14 miles west.
Under the town center the state geologic map shows Alluvium (silt, sand), from the Holocene, less than 12,000 years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 8×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Fine-detrital, coarse-detrital. Age: Pleistocene, less than 2.6 million years old. About 8 mi of the line.
Basalt. Age: Late Oligocene to Early Pliocene, 3.6 to 28 million years old. About 7 mi of the line.
Silt, sand. Age: Holocene, less than 12,000 years old. About 5 mi of the line.
Silt, sand. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Conglomerate, volcanic. Age: Middle Miocene to Pliocene, 2.6 to 16 million years old. About 1 mi of the line.
Silt. Age: Pleistocene, less than 2.6 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 Ahtanum reaches the Pacific Ocean by way of Bachelor Creek, Ahtanum Creek, the Yakima and the Columbia: about 450 river miles.
Lake on the way: Lake Umatilla.
210 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Ahtanum; river miles along the main stem, rounded.
Ahtanum has a cold semi-arid climate. Summer afternoons average 90° in July; winter nights fall to about 23° in December. A normal year brings about 20 inches of snow; with the rain, that comes to about 8 inches of water.
On November 14 Ahtanum normally reaches 50° and falls to 27°. The record high is 72°, in 2021; the record low 0°, in 1955. The most rain on this date, 0.66 in, fell in 2020.
Normals 1991–2020 and records since 1946 from the Yakima Area threaded record (Yakima Airport, 4 miles east, 180 ft lower). NOAA, through RCC-ACIS.
