Texas Geography, Climate & Nature

Texas covers 268,596 square miles, about 7 per cent of the United States, second only to Alaska, and is the southern end of the continent's central plains, which stop against Mexico's Sierra Madre Oriental. It borders Louisiana across the Sabine, Arkansas and Oklahoma across the Red River, New Mexico, and four Mexican states -- Chihuahua, Coahuila, Nuevo León and Tamaulipas -- across the Rio Grande, the fourth-longest river in North America at 1,896 miles, which forms the international line from El Paso to the Gulf and now delivers only a fifth of its water to the sea. The longest straight line, from the north-west corner of the Panhandle to the Rio Grande below Brownsville, is 801 miles; El Paso is closer to San Diego than to Houston. The Gulf coast runs 367 miles, paralleled by barrier islands that enclose some of the most productive estuaries in the country, with Padre Island, 113 miles long, the longest undeveloped barrier island in the world.

Physically the state has four regions from south-east to west: the Gulf Coastal Plains, the Interior Lowlands, the Great Plains Province and the Basin and Range. The visitor's map has more: the Piney Woods of East Texas, a temperate pine forest that includes the Big Thicket; the Hill Country of limestone and granite on the Edwards Plateau, bounded on the east by the Balcones Escarpment and cut by springs and flash floods, with Enchanted Rock's pink granite dome rising 425 feet; the Llano Estacado, the great tableland of the Panhandle and South Plains with nearly 22,000 playa lakes, into which Palo Duro Canyon drops 800 feet for 45 miles; and the Trans-Pecos, where the Chihuahuan Desert, the largest hot desert in North America, meets the mountains -- Guadalupe Peak, the highest point at 8,751 feet, the Davis Mountains around Marfa at 4,685 feet, and the Chisos inside Big Bend National Park, the only range in the country wholly within a national park. Ten climatic regions, eleven ecological regions, 3,700 named streams and 15 major rivers make the inventory.

The people live in the Texas Triangle: Houston, 2.3 million in the city and 7.8 million in the metropolis, the largest city in the South; Dallas and Fort Worth, whose metroplex of 8.5 million is the fourth-largest in the country and the largest inland one with no navigable link to the sea; San Antonio, 1.43 million, the seventh-largest American city; and Austin, the capital, 961,855 and the fastest-growing large city since 2010, 80 miles up Interstate 35 from San Antonio. Together with the interstates that join them they hold 17 million people, nearly three-quarters of the state. El Paso, 678,815, sits at the far western tip in a binational region of 2.7 million with Ciudad Juárez.

Texas's weather runs from humid in the east to arid in the west. The eastern half is humid subtropical: Houston averages 93 °F by day in July and 46 at night in January, with 56 inches of rain a year, and the Gulf coast has mild winters. The western half is semi-arid, and the far west arid: El Paso averages 96 °F in July and 35 at night in January, with under nine inches of rain and a little snow, and Big Bend's Panther Junction 92 and 37 with 13 inches. The Panhandle is colder, Amarillo dropping to 25 °F on January nights and taking 17 inches of snow a year, and snow falls several times each winter there and in the western mountains, once or twice in North Texas, and once every few years in the centre and east. The state record is 120 °F, set at Seymour in 1936 and equalled at Monahans in 1994.

Three hazards define the calendar. Texas leads the country in tornadoes, 139 a year, mostly in North Texas and the Panhandle in April, May and June. The Atlantic hurricane season runs from June to November, and the upper Texas coast has taken 56 per cent of the state's landfalls since 1851 -- the 1900 Galveston storm that killed at least 8,000, and Harvey in 2017, the wettest cyclone in American history at 60.58 inches near Beaumont. And with no barrier between Texas and the pole, Arctic air occasionally reaches the Gulf: Winter Storm Uri in February 2021 left more than three million without power. The Canadian advisory names heat from June to September as the season's danger and dehydration and heatstroke as fatal; the Hill Country adds flash floods, most recently in 2025.

Best Destinations by Month has the practical reading.

Texas holds eleven ecological regions, at least 268 grass species and 447 woody plants, and habitats from the Piney Woods -- a temperate pine forest the World Wide Fund for Nature ranks among the country's critically endangered ecoregions, with more than 300 bird species and the Big Thicket, a UNESCO biosphere reserve since 1974 with over 500 vertebrates -- through the coastal marshes and barrier islands to the Hill Country's live oak and Ashe juniper and the Chihuahuan Desert, the largest hot desert in North America and only 8,000 years old. Big Bend alone protects more than 1,200 plant species including 60 cacti, 450 birds, 56 reptiles, 75 mammals and about 3,600 insects; the Guadalupe Mountains over a thousand plants including an endemic violet; Enchanted Rock more than 500 on its granite. The bluebonnet is the state flower, and the 22,000 playa lakes of the High Plains are the largest such concentration on earth. Texas has fifteen native grape species, more than any region in the world.

The protected estate is federal and state: Big Bend National Park since 1944, 801,163 acres and one of the least-visited parks in the contiguous states; Guadalupe Mountains National Park since 1972, with 46,850 acres of wilderness; Padre Island National Seashore, 70 miles of the world's longest undeveloped barrier island on the Central Flyway, with 380 bird species, 45 per cent of North America's, and a Kemp's ridley turtle nesting programme since 1978; the Big Thicket National Preserve; Aransas National Wildlife Refuge, 115,324 acres since 1937 and the winter home of the whooping crane; Caddo Lake, a Ramsar wetland with one of the largest flooded cypress forests in the country; and Palo Duro Canyon, Enchanted Rock and the other state parks. The condor-scale story is the crane: 21 wild birds in 1941, about 560 now in the flock that winters at Aransas out of just over 830 alive.

The threats are water -- the Rio Grande reaching the Gulf at a fifth of its flow, the aquifers of the plains -- heat, the fires and floods of a warming state, the 2026 waiver of restrictions on border-wall construction through Big Bend, and the plain pressure of 31 million people. No fuller species inventory was consulted beyond the sources named in the data file.

The animals a visitor can plan on are the bats: twenty million Mexican free-tailed bats, the state's official flying mammal, pour out of Bracken Cave north of San Antonio from March to October on the conservation group's guided evenings, the largest concentration of mammals in the world, and up to 1.5 million emerge from under Austin's Congress Avenue Bridge on summer nights, the largest urban colony anywhere. The whooping crane, the tallest bird in North America, winters at Aransas on the coast from November to March and is watched from boats; the state's 380-species seashore at Padre and the Gulf marshes hold roseate spoonbills, herons, ibises and alligators. The Texas Longhorn, the state large mammal, descends from the cattle of Christopher Columbus's second voyage and carries horns of over eight feet; the nine-banded armadillo, nocturnal and given to jumping straight up when startled, is the roadside emblem; monarchs pass through every autumn on their way to Mexico.

Big Bend has black bears and mountain lions, and its safety page is exact: keep your distance, do not run, stand tall and shout if approached, report every sighting; it also has snakes, and the desert's real killers are heat and dehydration. The ocelot survives in the brush of the lower Rio Grande valley, where the first Texas specimen came from Brownsville in 1855; the black bear is nearly gone from the Piney Woods. Rabies may be present in wildlife including bats, the advisories note, so no bat is touched.