The smallest state west of the Appalachian Mountains, Indiana has three main land regions; the Great Lakes Plains in the north, the Till Plains in central Indiana, and the Southern Plains and Lowlands in the south.

The Great Lakes Plains is a fertile lowland that runs along the Great Lakes. Along Lake Michigan, there are large sand dunes and to the south there is rich black soil that is perfect for farming. There are also many small lakes and low hills. This area is sometimes referred to as the Northern Lake and Moraine Region. Moraines are low hills of earth and rocks left behind by melting glaciers at the end of the ice age.

The broad, fertile Till Plains are to the south of the Great Lakes Plains and are a part of the great Midwestern Corn Belt. The Till Plains also have many low hills and valleys. South of the Till Plains are the Southern Plains and Lowlands. Ice age glaciers did not advance into this area so it is the hilliest part of the state. There are also many steep hills, called knobs, divided by lowlands.

Indiana forms part of the east-central lowlands which slope down from the Appalachian Mountains to the Mississippi River. Thus, many of Indiana’s rivers drain into the Mississippi. The Wabash, the Ohio, and the east and west forks of the White River form part of the Mississippi basin. In the north the St. Joseph River meanders into Lake Michigan, while in the east the Maumee flows northeastward into Lake Erie. The northern half of the state is dotted with many small glacial lakes, including several of the state’s largest. The southern Plains and Lowlands contain several caverns, including Marengo and Wyandotte caves, which have been carved in the limestone by underground streams.

Indiana has a temperate climate. Although Indiana sometimes has temperatures below 0°F (–18°C) during the winter, the average temperatures in January are between 17°F (–8°C) and 35°F (2°C). Average temperatures during July vary from 63°F (17°C) to 88°F (31°C). The record high for the state was 116°F (47°C) set on 14 July 1936 at Collegeville; the record low was –36°F (–38°C) on 19 January 1994 at New Whiteland.

The climate of northwestern Indiana is affected by its location near Lake Michigan. Cold air passing over the warmer lake water in fall and winter causes heavy precipitation and heavy winter snowfall. The “lake effect” also causes warmer temperatures in the fall and cooler temperatures in spring than might be expected. Indiana is part of a belt of Midwestern states that have a lot of severe storms. In spring, a large number of tornadoes strike the state.