The Lapwai 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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77° on Nov. 12, 1999, the hottest reading for this week of the year since 1881. Next is 69° in 2021.
Lapwai’s center stands about 970 ft above sea level. Within three miles the land runs from 860 ft to 2,000 ft, a difference of 1,140 ft: steep hill country. The highest named summit within 15 miles is Culdesac Hill, about 3,020 ft, 8 miles east-southeast.
Under the town center the state geologic map shows Alluvial deposits (gravel, sand, silt), from the Quaternary, less than 2.6 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 6×. 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, basaltic-andesite. Age: Early Miocene to Late Miocene, 6 to 18 million years old. About 22 mi of the line.
Gravel, sand, silt. Age: Quaternary, less than 2.6 million years old. About 2 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 Lapwai reaches the Pacific Ocean by way of Lapwai Creek, the Clearwater, the Snake and the Columbia: about 470 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 Lapwai; river miles along the main stem, rounded.
Lapwai has a cold semi-arid climate. Summer afternoons average 91° in July; winter nights fall to about 30° in January. A normal year brings about 13 inches of snow; with the rain, that comes to about 13 inches of water.
On November 14 Lapwai normally reaches 49° and falls to 35°. The record high is 69°, in 2021; the record low −3°, in 1955. The most rain on this date, 0.84 in, fell in 1988.
Normals 1991–2020 and records since 1881 from the Lewiston Area threaded record (Lewiston Airport, 10 miles west-southwest, 460 ft higher). NOAA, through RCC-ACIS.
