The Seis Lagos 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 cloudy
Showers likely; cooler
Chance of showers; warmer
Partly cloudy
Partly cloudy
Partly cloudy
Mostly sunny
87° on Nov. 15, 2025, the hottest reading for this week of the year since 1946. Next is 84° in 2013.
Seis Lagos’s center stands about 560 ft above sea level. Within three miles the land runs from 480 ft to 630 ft, a difference of 150 ft: gently rolling country.
Under the town center the state geologic map shows Ozan Formation (claystone), from the Late Cretaceous, 66 to 72 million years old.
The section below crosses 6 rock units mapped at the surface.
Heights every 0.1 mile from the Copernicus GLO-90 surface model; vertical exaggeration about 62×. The colored band under the surface is the rock the state geologic map shows at the surface, not a picture of what lies beneath.
Marlstone, chalk. Age: Late Cretaceous, 66 to 100 million years old. About 9 mi of the line.
Claystone. Age: Late Cretaceous, 66 to 72 million years old. About 9 mi of the line.
Clay. Age: Late Cretaceous, 66 to 72 million years old. About 3 mi of the line.
Fine-detrital, coarse-detrital. Age: Holocene, less than 12,000 years old. About 2 mi of the line.
Sandstone-mudstone. Age: Late Cretaceous, 66 to 72 million years old. About 0.4 mi of the line.
Sand. Age: Pleistocene to Holocene, less than 2.6 million years old. About 0.3 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 Seis Lagos reaches Galveston Bay and the Gulf of America by way of Lavon Lake, the East Fork Trinity and the Trinity: about 470 river miles.
Lakes on the way: Woodlands Golf Course Lake, Lavon Lake and Corder Lake.
220 miles of the trip are on the Trinity.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Seis Lagos; river miles along the main stem, rounded.
Seis Lagos has a humid subtropical climate. Summer afternoons average 95° in August; winter nights fall to about 36° in January. About 42 inches of rain fall in a normal year.
Normals 1991–2020 and records since 1946 at Richardson, 11 miles west-southwest, 120 ft higher. NOAA, through RCC-ACIS.
