The Helena 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. 11, 2022, the hottest reading for this week of the year since 1979. Next is 69° in 2012.
Helena’s center stands about 740 ft above sea level. Within three miles the land runs from 570 ft to 940 ft, a difference of 370 ft: rolling country. The highest named summit within 15 miles is Mount Bundy, about 1,180 ft, 11 miles east-northeast.
Under the town center the state geologic map shows Ellsworth Shale, from the Late Devonian, 359 to 384 million years old.
The section below crosses 3 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 23×. 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 Devonian, 359 to 384 million years old. About 11 mi of the line.
Shale. Age: Carboniferous, 324 to 359 million years old. About 9 mi of the line.
Black-shale. Age: Late Devonian, 359 to 384 million years old. About 1 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 Helena reaches Lake Michigan by way of Torch Lake and the Torch: about 17 river miles. From there it moves on through the Great Lakes, over Niagara Falls and down the St. Lawrence to the Atlantic.
Lakes on the way: Torch Lake and Elk Lake.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Helena; river miles along the main stem, rounded.
Helena has a warm-summer humid continental climate. Summer afternoons average 80° in July; winter nights fall to about 16° in February. About 31 inches of rain fall in a normal year.
On November 14 Helena normally reaches 47° and falls to 33°. The record high is 62°, in 2005; the record low 14°, in 1986. The most rain on this date, 0.46 in, fell in 2024.
Normals 1991–2020 and records since 1979 at Old Mission 3 SSW, 12 miles west. NOAA, through RCC-ACIS.
