Physical Geography

Alabama occupies parts of three major physiographic regions of the United States: the Gulf Coastal Plain, the Appalachian Highlands, and the Central Lowlands.

The Gulf Coastal Plain, the largest of the three, covers most of western and southern Alabama. It begins as a narrow neck of flat terrain near the coast and rises gradually in a series of almost parallel terraces, cuestas (escarpment-like ridges), and hills toward the north. The Black Belt region, named for its rich soil, stretches across the central section of the state and is the most extensive level part.

The Appalachian Highlands, in the northeast, extend diagonally from Georgia and Tennessee into the central part of the state. This southern tip of the Appalachians includes the broad, hilly Cumberland Plateau; the low, parallel ridges and intervening valleys of the Ridge and Valley region; and the eroded Piedmont Plateau. Marking the southern limit of the highlands is the fall line, a belt of sloping land leading down to the Gulf Coastal Plain. The highest point in the state is Cheaha Mountain, 2,407 feet (734 m) above sea level.

The Central Lowlands section of Alabama is a narrow belt of land in the northwest along the Tennessee border. Structurally, it is part of a low, rolling plateau that forms the southern rim of the Nashville Basin in Tennessee.

Alabama lies in one of the rainiest parts of the continent, and is drained by numerous rivers. The Alabama River system, including the Coosa and Tallapoosa rivers in east-central Alabama, flows diagonally across the state to join the Mobile River near the coast. The Black Warrior–Tombigbee Waterway also empties into the Mobile, which continues on to Mobile Bay, an arm of the Gulf of Mexico. These systems, along with that of the Tennessee, which loops across the north, drain most of the state. The southeast is drained by the Pea, Conecuh, and Chattahoochee rivers.

There are few natural lakes in Alabama. Most of the large inland bodies of water are reservoirs, created by damming rivers. The largest of these are Wheeler and Wilson lakes, in the Muscle Shoals area of the Tennessee River; Guntersville and Pickwick lakes, also on the Tennessee; Lake Martin, on the Tallapoosa; Weiss Lake, on the Coosa; and Walter F. George Reservoir, on the Chattahoochee.

Alabama has a humid subtropical climate that becomes more temperate with distance from the coast and with increased elevation in the Appalachians. Chief distinguishing marks are long, hot, and humid summers, relatively mild winters, and abundant rainfall. Average July temperatures range from about 81° F. (27° C.) near the coast to 78° F. (26° C.) in the northeast. Winters, though seldom cold, are made variable by alternating cool air masses from the continental interior and warm, moist air masses from the Gulf of Mexico. Average January temperatures vary from 54° F. (12° C.) near the coast to 42° F. (6° C.) in the highlands.

Precipitation, mostly rain, is moderately heavy and well distributed throughout the year. The greatest amount, 64 inches (1,625 mm) annually, occurs near the coast. Elsewhere it varies from 48 to 55 inches (1,220 to 1,400 mm). An average of three inches (76 mm) of snow falls in the highlands; in other areas snow is almost unknown. Among the severe storms that occasionally strike Alabama are tornadoes, between November and May, and hurricanes, between July and November.