The Janesville 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.
Sunny
Mostly sunny; warmer
Mostly sunny
Mostly sunny
Partly cloudy
Mostly sunny
Chance of showers
75° on Nov. 11, 2022, the hottest reading for this week of the year since 1987. Next is 71° in 1989.
Janesville’s center stands about 880 ft above sea level. Within three miles the land runs from 770 ft to 1,010 ft, a difference of 240 ft: rolling country. The highest named summit within 15 miles is Mount Zion, about 1,080 ft, 8 miles east.
Under the town center the state geologic map shows Ancell Group (sandstone), from the Ordovician, 445 to 487 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 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.
Sandstone. Age: Ordovician, 445 to 487 million years old. About 12 mi of the line.
Dolostone. Age: Ordovician, 445 to 487 million years old. About 11 mi of the line.
Sandstone. Age: Cambrian, 487 to 542 million years old. About 1 mi of the line.
Dolostone. Age: Early Ordovician, 471 to 487 million years old. About 0.4 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 Janesville reaches the Gulf of America by way of Marsh Creek, the Rock River and the Mississippi: about 1,640 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Janesville; river miles along the main stem, rounded.
Janesville has a hot-summer humid continental climate. Summer afternoons average 84° in July; winter nights fall to about 12° in January. A normal year brings about 37 inches of snow; with the rain, that comes to about 37 inches of water.
On November 14 Janesville normally reaches 47° and falls to 29°. The record high is 70°, in 1999; the record low 10°, in 1996. The most rain on this date, 0.65 in, fell in 2001.
Normals 1991–2020 and records since 1987 at Afton - Janesville Wwtp, 6 miles south, 120 ft lower. NOAA, through RCC-ACIS.
