South Texas is a geographic and cultural region of the U.S. state of Texas that lies roughly south of—and includes—San Antonio. The southern and western boundary is the Rio Grande, and to the east it is the Gulf of Mexico. The population of this region is about 4.96 million according to the 2017 census estimates.[1] The southern portion of this region is often referred to as the Rio Grande Valley. The eastern portion along the Gulf of Mexico is also referred to as the Coastal Bend.
Greater Houston and Beaumont–Port Arthur are occasionally tied to the region, both for physically being on the southern end of the state and for businesses that use "South Texas" in its name. (i.e. South Texas School of Law, South Texas State Fair, etc). However, the two are more commonly associated with East Texas or Southeast Texas.
There is no defined northern boundary, although it is believed to be at the city of San Antonio and from an east to west line extending from the Rio Grande near Maverick County to the Gulf of Mexico, but turning southeast at or near Lavaca County, and continuing towards the Gulf of Mexico to separate it from East Texas and Southeast Texas. The Rio Grande serves as the western and southern boundaries and separates Texas from Mexico. The eastern portion of South Texas is bordered by the Gulf of Mexico. South Texas consists of 41 counties. Its terrain is flat, lying on the coastal plain. South Texas is so vast, that there are even subregions. The very southern tip of South Texas, called the Rio Grande Valley, has fertile soils and is known for its citrus production. The eastern portion of South Texas is often referred to as the Coastal Bend; here, coastal salt marshes, estuaries, and wetlands are scattered all around. The western and central parts are known as the South Texas Plains or the Brush Country. Mesquite trees and crop fields dominate the Brush Country.[citation needed]
Some people consider Houston to be in South Texas for several reasons: numerous businesses in the Houston region contain 'South Texas' in their titles.[2] The United States District Court for the Southern District of Texas includes the Houston division. However, Houston is most accurately classified as being within Southeast Texas, a subregion of East Texas.
The climate of South Texas is varied. The area along the Mexican border is generally semi-arid (Köppen climate classification BSh), while the area from the coast inland to just west of San Antonio has a humid subtropical climate (Köppen Cfa). South Texas weather is affected by the Sierra Madre Oriental mountains to the west, the Gulf of Mexico to the east, and the Chihuahuan Desert to the west/northwest. Moisture from the Pacific is cut off by the Mexican Sierra Madre Occidental and Oriental mountain ranges. Along the coast the climate is best exemplified in the summers when humidity is extremely high though at times arid, depending upon whether tropical moisture from the Gulf and sometimes from the Pacific is flowing in or if the region is cut off from any moisture by high pressure systems, causing long droughts, which occur every few years. Temperatures reach freezing only a few times in the winter and snowfall is rare, usually three inches or less. Summers in this zone are hot and humid, with daily averages above 90 °F or 32.2 °C. In addition, areas in Texas that are slightly inland from the Gulf of Mexico, such as San Antonio that border the semi-arid climate zone, generally see a peak of precipitation in the spring, and a deep, drought-like nadir in midsummer. The region itself sees a short wet season from March to May and another one from late August to October, and a dry season elsewhere in the year. Night-time temperatures are around 85 °F or 29.4 °C in summer. The region of South Texas includes the semi-arid ranch country and the wetter Rio Grande Valley. Considered to be the southernmost tip of the American Great Plains region, the inland region has rainfall similar to that of the Northern Plains. The coastal areas are warm most of the year due to currents of the Gulf of Mexico, but can get cold in winter if a strong front comes in, occasionally causing snow at sea level. Rain in the coastal region is more abundant than in the inland region, and subtropical forests line the Rio Grande. Inland, where it is drier, ranches dominate the landscape, characterized by thick, spiny brush and grasslands. The winters in the inland region are cooler and drier, as Arctic air can make it into the region, but snow is rare due to the lack of humidity. Summers are for the most part hot and dry, but at times can be humid if winds come off the warmer Gulf of Mexico. Tornadoes can occur in this region, but less frequently than in other parts of the state.