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.
Partly cloudy
Showers likely
Showers likely
Mostly sunny
Showers likely
Showers likely
Partly cloudy
71° on Nov. 13, 1995, the hottest reading for this week of the year since 1893. Next is 69° in 1896.
Janesville’s center stands about 4,240 ft above sea level. Within three miles the land runs from 4,050 ft to 6,910 ft, a difference of 2,860 ft: mountain country. The highest named summit within 15 miles is Thompson Peak, about 7,740 ft, 3 miles southwest.
Under the town center the state geologic map shows Quaternary alluvium and marine deposits (coarse-detrital), from the Pleistocene to Holocene, less than 2.6 million years old.
The section below crosses 5 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 5×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Coarse-detrital. Age: Pleistocene to Holocene, less than 2.6 million years old. About 14 mi of the line.
Sandstone. Age: Eocene, 34 to 56 million years old. About 3 mi of the line.
Granodiorite. Age: Permian to Tertiary, 2.6 to 260 million years old. About 3 mi of the line.
Andesite. Age: Late Oligocene to Pleistocene, 2 to 24 million years old. About 2 mi of the line.
Mafic-volcanic, felsic-volcanic. Age: Permian to Jurassic, 145 to 260 million years old. About 0.8 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.
Rain that falls on Janesville runs straight into Honey Lake. Honey Lake has no outlet to the sea: the water leaves only by evaporating or soaking into the ground.
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 warm-summer Mediterranean climate. Summer afternoons average 88° in July; winter nights fall to about 22° in January. About 13 inches of rain fall in a normal year.
On November 14 Janesville normally reaches 52° and falls to 28°. The record high is 68°, in 1995; the record low 1°, in 1985. The most rain on this date, 1.58 in, fell in 1903.
Normals 1991–2020 and records since 1893 at Susanville 2 SW, 11 miles northwest. NOAA, through RCC-ACIS.
