The Sienna 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
Showers likely
Showers likely; cooler
Mostly sunny
Partly cloudy
Partly cloudy
Partly cloudy
90° on Nov. 16, 2025, the hottest reading for this week of the year since 1930. Next is 87° in 2005.
Sienna’s center stands about 70 ft above sea level. Within three miles the land runs from 40 ft to 100 ft, a difference of 60 ft: nearly flat ground.
Under the town center the state geologic map shows Alluvium (fine-detrital, coarse-detrital), from the Holocene, less than 12,000 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.
Fine-detrital, coarse-detrital. Age: Holocene, less than 12,000 years old. About 12 mi of the line.
Sand. Age: Pleistocene, less than 2.6 million years old. About 6 mi of the line.
Clay, silt. Age: Pleistocene, less than 2.6 million years old. About 6 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 Sienna reaches the Gulf of America by way of Oyster Creek: about 95 river miles.
Traced down the USGS NHDPlus V2.1 river network from the Census center point of Sienna; river miles along the main stem, rounded.
Sienna has a humid subtropical climate. Summer afternoons average 93° in July; winter nights fall to about 46° in January. About 56 inches of rain fall in a normal year.
On November 14 Sienna normally reaches 73° and falls to 54°. The record high is 86°, in 2025; the record low 31°, in 1940. The most rain on this date, 2.76 in, fell in 1998.
Normals 1991–2020 and records since 1930 at Houston William P Hobby Airport, 17 miles northeast. NOAA, through RCC-ACIS.
