The Acton 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 1934. Next is 71° in 1990.
Acton’s center stands about 3,800 ft above sea level. Within three miles the land runs from 3,530 ft to 4,010 ft, a difference of 480 ft: hilly country.
Under the town center the state geologic map shows Bearpaw Formation (shale), from the Late Cretaceous, 72 to 84 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 19×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Shale. Age: Late Cretaceous, 72 to 84 million years old. About 11 mi of the line.
Sandstone, shale. Age: Late Cretaceous, 72 to 84 million years old. About 8 mi of the line.
Shale. Age: Late Cretaceous, 72 to 84 million years old. About 3 mi of the line.
Sandstone. Age: Late Cretaceous, 66 to 84 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.
Acton has a hot-summer humid continental climate. Summer afternoons average 87° in July; winter nights fall to about 18° in January. A normal year brings about 57 inches of snow; with the rain, that comes to about 14 inches of water.
On November 14 Acton normally reaches 46° and falls to 27°. The record high is 70°, in 1999; the record low −10°, in 1955. The most rain on this date, 0.49 in, fell in 1961.
Normals 1991–2020 and records since 1934 from the Billings Area threaded record (Billings International Airport, 11 miles southeast, 210 ft lower). NOAA, through RCC-ACIS.
