The San Juan 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
Mostly sunny; warmer
Chance of showers; cooler
Mostly cloudy
Mostly cloudy; warmer
Partly cloudy
Partly cloudy
33° on Nov. 14, 2018, the coldest reading for this week of the year since 1941. Next is 34° in 1970.
San Juan’s center stands about 110 ft above sea level. Within three miles the land runs from 80 ft to 120 ft, a difference of 40 ft: nearly flat ground.
Under the town center the state geologic map shows Beaumont Formation, areas predominantly clay (clay, silt), from the Pleistocene, 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 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.
Sand. Age: Holocene, less than 12,000 years old. About 8 mi of the line.
Clay, silt. Age: Pleistocene, less than 2.6 million years old. About 8 mi of the line.
Fine-detrital, sand. Age: Pleistocene to Holocene, less than 2.6 million years old. About 4 mi of the line.
Silt, sand, clay. Age: Pleistocene, less than 2.6 million years old. About 2 mi of the line.
Silt, clay. Age: Holocene, less than 12,000 years old. About 2 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.
San Juan has a hot semi-arid climate. Summer afternoons average 100° in August; winter nights fall to about 53° in January. About 22 inches of rain fall in a normal year.
On November 14 San Juan normally reaches 80° and falls to 60°. The record high is 93°, in 1989; the record low 33°, in 2018. The most rain on this date, 0.20 in, fell in 1959.
Normals 1991–2020 and records since 1941 from the McAllen Area threaded record (Mcallen Miller International Airport, 6 miles west). NOAA, through RCC-ACIS.
