Oklahoma Geography, Climate & Nature

Oklahoma is a landlocked state in the South Central United States, bordered by Texas to the southwest and south, Kansas to the north, Missouri to the northeast, Arkansas to the southeast, New Mexico to the west and Colorado to the northwest. It sits in the plains and U.S. Interior Highlands near the geographic center of the 48 contiguous states, and contains ten distinct ecological regions, more per square mile than any other state.

Four mountain ranges cross Oklahoma: the Arbuckle and Wichita Mountains in the south-central and southwest, and the Ozark and Ouachita Mountains in the east, part of the U.S. Interior Highlands, one of the few major highland regions between the Rockies and the Appalachians. Black Mesa, in the far northwest corner of the panhandle, is the state's highest point at 4,368 feet; the lowest, 289 feet, is on the Little River in the southeast. More than 500 named creeks and rivers cross the state, and with over 200 reservoirs built by dams, many constructed after the 1930s Dust Bowl drought, Oklahoma has more artificial lakes than any other U.S. state. The state is traditionally divided into seven regions: Green Country (northeast), Choctaw Country (southeast), Frontier Country (central), Chickasaw Country (south-central), Great Plains Country (southwest), Red Carpet Country (northwest) and the Oklahoma Panhandle.

Oklahoma's climate ranges from humid subtropical in the wetter, forested east to semi-arid in the drier panhandle west, a transition that also shapes the state's ten distinct ecological regions. Summers are hot and often humid statewide, with temperatures regularly exceeding 90°F from June through August; winters are generally mild, though the western and panhandle areas see colder, drier conditions and occasional ice storms.

Oklahoma lies within Tornado Alley, the loosely defined swath of the central United States most prone to tornadoes; through 2007 data, Oklahoma ranked second nationally, after Kansas, in tornadoes per unit area. The state's severe-weather season runs roughly April through June, when supercell thunderstorms and tornadoes are most frequent. The 1930s brought the Dust Bowl, a severe, multi-year drought worsened by agricultural practices that stripped topsoil across the southern Plains, including much of western Oklahoma, and led directly to the construction of the state's many dam-built reservoirs.

Oklahoma's ten distinct ecological regions, more concentrated per square mile than any other U.S. state, run from the tallgrass prairie of the north-central plains to the pine and hardwood forests of the Ouachita Mountains in the southeast, which cover 24 percent of the state overall. The Tallgrass Prairie Preserve in north-central Oklahoma protects the largest remaining area of tallgrass prairie anywhere in the world, a once-vast ecosystem that historically spanned 14 states and now survives on roughly 10 percent of its former range.

The Wichita Mountains Wildlife Refuge, established in 1901 and the oldest managed wildlife facility in the U.S. Fish and Wildlife Service system, protects one of the state's most distinctive landscapes: granite mountains roughly 500 million years old rising from mixed-grass prairie, home to 806 plant species, 240 bird species, and dozens of fish, reptile and amphibian species across its protected acreage. The Ouachita National Forest, extending into the state's southeast, is the oldest and largest national forest in the southern United States.

The Wichita Mountains Wildlife Refuge is Oklahoma's premier wildlife destination, home to free-roaming American bison, elk and Texas longhorn cattle across its protected grassland and granite terrain, alongside prairie dogs, badgers and armadillos typical of the state's shortgrass and mixed-grass prairie ecosystems. Some of the nation's largest prairie dog towns occupy the shortgrass prairie of the Oklahoma Panhandle.

The state's prairies also support greater prairie-chickens and abundant waterfowl on its more than 200 reservoirs, while bald eagles hunt along rivers such as the Arkansas through Tulsa in winter months. The tallgrass and mixed-grass prairie ecosystems, though reduced to a fraction of their historic extent, remain a stronghold for grassland bird species increasingly rare elsewhere in North America.