The Lake Forest 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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9° on Nov. 12, 2019, the coldest reading for this week of the year since 1996. Next is 11° in 2014.
Lake Forest’s center stands about 710 ft above sea level. Within three miles the land runs from 570 ft to 740 ft, a difference of 170 ft: gently rolling country.
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 13 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.
Lake Forest straddles the St. Lawrence Divide. Rain on the east side runs to Lake Michigan; most of the rest goes to the Gulf of America.
From the center of town, a raindrop reaches the Gulf of America by way of the Skokie, the North Branch Chicago, the Chicago Sanitary and Ship Canal, the Des Plaines, the Illinois and the Mississippi: about 1,550 river miles. Rain that falls on Lake Forest runs straight into Lake Michigan. From there it moves on through the Great Lakes, over Niagara Falls and down the St. Lawrence to the Atlantic.
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 Lake Forest; river miles along the main stem, rounded.
Lake Forest has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 19° in January. About 32 inches of rain fall in a normal year.
On November 14 Lake Forest normally reaches 49° and falls to 34°. The record high is 67°, in 2025; the record low 15°, in 1996. The most rain on this date, 0.19 in, fell in 2020.
Normals 1991–2020 and records since 1996 at Chicago Palwaukee Airport, 10 miles south-southwest. NOAA, through RCC-ACIS.
