The Avon 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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73° on Nov. 12, 1999, the hottest reading for this week of the year since 1893. Next is 70° in 1990.
Avon’s center stands about 5,270 ft above sea level. Within three miles the land runs from 4,680 ft to 5,510 ft, a difference of 830 ft: hilly country. The highest named summit within 15 miles is Black Mountain, about 8,320 ft, 8 miles north-northeast.
Under the town center the state geologic map shows Rhyolite, from the Tertiary, 2.6 to 66 million years old.
The section below crosses 8 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.
Age: Tertiary, 2.6 to 66 million years old. About 5 mi of the line.
Metasiltstone, argillite, quartzite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 4 mi of the line.
Andesite, latite. Age: Late Cretaceous, 72 to 84 million years old. About 4 mi of the line.
Sedimentary. Age: Tertiary, 2.6 to 66 million years old. About 3 mi of the line.
Andesite, basalt. Age: Tertiary, 2.6 to 66 million years old. About 2 mi of the line.
Metasiltstone, argillite. Age: Mesoproterozoic, 1 to 1.6 billion 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. 2 smaller units 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 Avon reaches the Pacific Ocean by way of Warm Spring Creek, the Little Blackfoot, the Clark Fork, the Pend Oreille and the Columbia: about 1,180 river miles.
Lakes on the way: Lake Pend Oreille, Lake Umatilla and Noxon Rapids Reservoir.
460 miles of the trip are on the Columbia.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Avon; river miles along the main stem, rounded.
Avon has a warm-summer humid continental climate. Summer afternoons average 79° in July; winter nights fall to about 11° in January. About 15 inches of rain fall in a normal year.
On November 14 Avon normally reaches 41° and falls to 17°. The record high is 68°, in 2025; the record low −18°, in 1959. The most rain on this date, 0.20 in, fell in 1903.
Normals 1991–2020 and records since 1893 from the Deer Lodge Area threaded record (Deer Lodge 3 W, 20 miles south-southwest, 430 ft lower). NOAA, through RCC-ACIS.
