The Lemont 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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7° on Nov. 12, 2019, the coldest reading for this week of the year since 1992. Next is 11° in 2014.
Lemont’s center stands about 610 ft above sea level. Within three miles the land runs from 570 ft to 780 ft, a difference of 210 ft: rolling country. The highest named summit within 15 miles is Mount Hoy, about 810 ft, 14 miles northwest.
Under the town center the state geologic map shows Silurian System undivided (dolostone, limestone), from the Silurian, 422 to 445 million years old.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 64×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Dolostone, limestone. Age: Silurian, 422 to 445 million years old. About 24 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 Lemont reaches the Gulf of America by way of the Des Plaines, the Illinois and the Mississippi: about 1,490 river miles.
Lake on the way: Peoria Lake.
1,190 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Lemont; river miles along the main stem, rounded.
Lemont has a hot-summer humid continental climate. Summer afternoons average 85° in July; winter nights fall to about 16° in January. A normal year brings about 33 inches of snow; with the rain, that comes to about 41 inches of water.
On November 14 Lemont normally reaches 50° and falls to 32°. The record high is 67°, in 2025; the record low 16°, in 2018. The most rain on this date, 0.30 in, fell in 2002.
Normals 1991–2020 and records since 1992 at Romeoville Wfo, 6 miles southwest. NOAA, through RCC-ACIS.
