The Florissant 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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−12° on Nov. 16, 1997, the coldest reading for this week of the year since 1948. Next is −9° in 2014.
Florissant’s center stands about 8,190 ft above sea level. Within three miles the land runs from 8,070 ft to 8,930 ft, a difference of 860 ft: hilly country. The highest named summit within 15 miles is Sentinel Point, about 12,460 ft, 12 miles southeast.
Under the town center the state geologic map shows Oligocene sedimentary rocks (sandstone), from the Eocene to Oligocene, 23 to 56 million years old.
The section below crosses 7 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.
Granite, alkali-feldspar-granite. Age: Mesoproterozoic, 1 to 1.6 billion years old. About 12 mi of the line.
Biotite-gneiss, schist, migmatite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 4 mi of the line.
Granite. Age: Paleoproterozoic, 1.6 to 2.5 billion years old. About 3 mi of the line.
Sandstone. Age: Eocene to Oligocene, 23 to 56 million years old. About 2 mi of the line.
Sandstone, conglomerate. Age: Miocene to Pliocene, 2.6 to 23 million years old. About 1 mi of the line.
Volcanic. Age: Late Eocene, 35 to 36 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. 1 smaller unit along the line are not listed.
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 Florissant reaches the Gulf of America by way of Twin Creek, the South Platte, the Platte, the Missouri and the Mississippi: about 2,480 river miles.
1,170 miles of the trip are on the Mississippi.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Florissant; river miles along the main stem, rounded.
Florissant has a cold semi-arid climate. Summer afternoons average 77° in July; winter nights fall to about −1° in January. A normal year brings about 50 inches of snow; with the rain, that comes to about 11 inches of water.
On November 14 Florissant normally reaches 45° and falls to 16°. The record high is 61°, in 1999; the record low −8°, in 1961. The most rain on this date, 0.26 in, fell in 1985.
Normals 1991–2020 and records since 1948 at Lake George 8 SW, 10 miles west-southwest, 290 ft higher. NOAA, through RCC-ACIS.
