The Pomona 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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82° on Nov. 14, 1999, the hottest reading for this week of the year since 1963. Next is 81° in 2016.
Pomona’s center stands about 970 ft above sea level. Within three miles the land runs from 910 ft to 1,100 ft, a difference of 190 ft: gently rolling country. The highest named summit within 15 miles is Chippewa Hills, about 1,160 ft, 5 miles east-southeast.
Under the town center the state geologic map shows Douglas Group (shale, sandstone), from the Carboniferous, 299 to 324 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 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.
Limestone, shale. Age: Carboniferous, 299 to 324 million years old. About 12 mi of the line.
Shale, sandstone. Age: Carboniferous, 299 to 324 million years old. About 11 mi of the line.
Sand, silt, clay. Age: Pleistocene to Holocene, less than 2.6 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 Pomona reaches the Gulf of America by way of the Marais des Cygnes, the Osage, the Missouri and the Mississippi: about 1,730 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 Pomona; river miles along the main stem, rounded.
Pomona has a hot-summer humid continental climate. Summer afternoons average 90° in July; winter nights fall to about 22° in January. About 39 inches of rain fall in a normal year.
On November 14 Pomona normally reaches 56° and falls to 35°. The record high is 82°, in 1999; the record low 8°, in 1986. The most rain on this date, 0.40 in, fell in 1980.
Normals 1991–2020 and records since 1963 at Pomona Lake, 6 miles west-northwest. NOAA, through RCC-ACIS.
