Parts of two great physiographic regions of North America—the Central Lowlands and the Great Plains—lie within North Dakota. Nearly everywhere the terrain is flat to rolling. Grassy prairies prevail in the east, more sparsely covered plains in the west. Much of the state was glaciated during the last Ice Age, when enormous glaciers moved southward, scouring and eroding the land. On retreating, the glaciers left thick coverings of glacial debris, often as distinctive landforms.

The Central Lowlands begin in the east at the Red River Valley, a plain 10 to 60 miles (16 to 97 km) wide that runs the width of the state. It is fertile, almost perfectly flat land, having once been part of the bed of glacial Lake Agassiz. In the north, where the Red River enters Canada, is the lowest point in the state—750 feet (229 m) above sea level. At the western edge of the valley are clusters of sandhills and a sharp escarpment leading to a glaciated upland, called the Drift Prairie.

The Drift Prairie is a region of relatively flat to gently rolling land that extends westward to within 50 to 60 miles (80 to 97 km) of the Missouri River. Here the surface consists of a thick mantle of drift, which is glacier-deposited material ranging in size from boulders to sand and clay. On the Canadian border is the region's most prominent feature —the Turtle Mountains, a drift-covered mesa rising 400 to 600 feet (120 to 180 m) above the level of the surrounding land. Also distinctive is the Souris Plain, southwest of the Turtle Mountains. It is a flat lacustrine (lake bed) plain that resembles the Red River Valley.

The Great Plains rise from the Drift Prairie along an escarpment, 300 to 400 feet (90 to 120 m) high, extending north and east of the Missouri River. Between the river and the escarpment lies the Missouri Coteau, a region of stony hills, marking the farthest advance of the Ice Age glaciers in North Dakota.

Beyond the Missouri River stretches an unglaciated section of the Great Plains, known locally as the Slope and also called the Missouri Plateau. It is predominantly a land of high rolling plains, flat-topped mesas and buttes, and deeply eroded river valleys. Especially eroded and rough are the badlands that border the Little Missouri River and its tributaries in the southwest. Other distinctive features include the Killdeer Mountains and White Butte, whose 3,506- foot (1,069-m) summit is the highest point in the state.

Drainage is either to the Gulf of Mexico by way of the Missouri-Mississippi river system or northward to Hudson Bay by the Red River of the North and Nelson River system. The divide between these two drainage basins runs in a northerly arching course between the northwestern and southwestern corners of the state.

The Missouri River flows southeasterly in North Dakota and is joined by the Yellowstone, Little Missouri, Knife, Heart, and Cannonball rivers. The James, also a tributary of the Missouri, flows southward through eastern North Dakota. Forming most of the North Dakota-Minnesota boundary is the Red River of the North. Into it flow the Sheyenne and Pembina. Also important is the Mouse (or Souris) River, which loops southward through the state from Canada.

Two reservoirs on the Missouri River—Lake Sakakawea and Lake Oahe—account for the bulk of the state's inland water. Lake Sakakawea, impounded by an earth dam two miles (3.2 km) long, extends some 200 miles (320 km) upstream and is North Dakota's largest body of water. These major reservoirs and many smaller ones, most of which are part of the Missouri River Basin project, provide hydroelectric power and irrigation water and, in addition, are used for flood control and recreational purposes. There are also hundreds of small glacial lakes. Many of these, including Devils Lake, have no outlet and contain brackish water.

North Dakota has a continental climate with long, cold winters and short summers that range from warm to hot. It is a relatively severe climate, known for an extremely large range of temperature. Chief influence on the climate is the state's middle-latitude location at the center of the continent, far removed from the tempering influences of large bodies of water.

January temperatures average between 1° and 15° F. (-17° and -9° C.), the increase being roughly from northeast to southwest. There are usually many days with temperatures below 0° F. (-18° C.) each winter. July is the warmest month and averages near 70° F. (21° C.) throughout the state. Occasionally there are days when the temperature reaches 90° to 100° F. (32° to 38° C.).

Precipitation is light to moderate, ranging from about 20 inches (510 mm) a year in the east to 13 inches (330 mm) in the west. Most of it comes during the growing season. Snow begins to fall as early as September and totals slightly more than 30 inches (760 mm) a year. Among the storms that occasionally strike the state are blizzards; tornadoes; violent thunderstorms; and wind, dust, and hail storms.

Natural Vegetation consists of medium to tall varieties of prairie grass in the eastern part of the state to shorter varieties in the west. Because of crop cultivation, little remains of the native grasslands. The chief exception is the national grassland administered by the National Forest Service in the badlands area of the southwest. Trees grow mainly along rivers, where water is sufficient to sustain them.