The Mertzon 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.
Chance of showers
Showers likely
Mostly cloudy; cooler
Partly cloudy
Mostly cloudy
Partly cloudy
Partly cloudy
90° on Nov. 14, 2025, the hottest reading for this week of the year since 1907. Next is 88° in 1989.
Mertzon’s center stands about 2,220 ft above sea level. Within three miles the land runs from 2,150 ft to 2,560 ft, a difference of 410 ft: hilly country. The highest named summit within 15 miles is Ketchum Mountain, about 2,730 ft, 15 miles west-northwest.
Under the town center the state geologic map shows Edwards Limestone, from the Early Cretaceous, 100 to 113 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 29×. 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. Age: Early Cretaceous, 100 to 113 million years old. About 18 mi of the line.
Coarse-detrital, fine-detrital. Age: Quaternary, less than 2.6 million years old. About 5 mi of the line.
Sandstone, claystone. Age: Early Cretaceous, 100 to 145 million years old. About 1 mi of the line.
Fine-detrital, coarse-detrital. Age: Holocene, less than 12,000 years old. About 0.9 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 Mertzon reaches the Gulf of America by way of Spring Creek, the South Concho, the Concho and the Colorado: about 720 river miles.
Lakes on the way: Buchanan Lake, Lake Marble Falls, Lake Lyndon B Johnson and Twin Buttes Reservoir.
320 miles of the trip are on the Colorado.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Mertzon; river miles along the main stem, rounded.
Mertzon has a humid subtropical climate. Summer afternoons average 97° in July; winter nights fall to about 34° in January. About 21 inches of rain fall in a normal year.
On November 14 Mertzon normally reaches 70° and falls to 43°. The record high is 90°, in 2025; the record low 18°, in 1976. The most rain on this date, 3.25 in, fell in 1934.
Normals 1991–2020 and records since 1907 from the San Angelo Area threaded record (San Angelo Mathis Field Airport, 20 miles east-northeast, 310 ft lower). NOAA, through RCC-ACIS.
