The Sylvan 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.
Mostly sunny
Mostly sunny; warmer
Partly cloudy
Mostly sunny
Partly cloudy
Mostly sunny
Showers likely
71° on Nov. 13, 1999, the hottest reading for this week of the year since 1893. Next is 70° in 1953.
Sylvan’s center stands about 1,240 ft above sea level. Within three miles the land runs from 860 ft to 1,250 ft, a difference of 390 ft: rolling country.
Under the town center the state geologic map shows Prairie du Chien Group (dolostone), from the Early Ordovician, 471 to 487 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 33×. 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. Age: Early Ordovician, 471 to 487 million years old. About 16 mi of the line.
Sandstone. Age: Cambrian, 487 to 542 million years old. About 7 mi of the line.
Sandstone. Age: Ordovician, 445 to 487 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 Sylvan reaches the Gulf of America by way of West Branch Mill Creek, Mill Creek, the Wisconsin and the Mississippi: about 1,670 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Sylvan; river miles along the main stem, rounded.
Sylvan has a warm-summer humid continental climate. Summer afternoons average 79° in July; winter nights fall to about 6° in January. A normal year brings about 47 inches of snow; with the rain, that comes to about 38 inches of water.
On November 14 Sylvan normally reaches 42° and falls to 25°. The record high is 67°, in 1990; the record low −9°, in 1916. The most rain on this date, 1.60 in, fell in 1927.
Normals 1991–2020 and records since 1893 at Viroqua, 16 miles northwest. NOAA, through RCC-ACIS.
