In the early 19th century Indiana was almost entirely covered with the deciduous hardwood forests common to the eastern United States.The nonforested portion of the state, primarily in the northwestern corner, consisted of grasslands—an extension into Indiana of the central Great Plains.
Aside from white-tailed deer, the population of which has been revived largely as a result of government conservation efforts, smaller mammals such as opossums, skunks, raccoons, rabbits, moles, shrews, and bats are abundant throughout the state.
The highest elevation is near the Ohio border, at about 1,250 feet (380 metres) above sea level, while the lowest point, at roughly 330 feet (100 metres), is in the southwest where the Wabash River enters the Ohio River.
About 90 percent of the land lies between 500 and 1,000 feet (150 and 300 metres).
In January, daily temperatures in Jeffersonville, on the Ohio River in the south, usually rise from the low 20s F (about –6 °C) into the low 40s F (about 4 °C), while in South Bend, near Lake Michigan in the north, temperatures typically range from the mid-10s F (about −9 °C) to the low 30s F (about −1 °C).
In July, temperatures in both the north and the south normally drop into the mid-60s F (about 17 °C) and rise into the mid- to upper 80s F (28–32 °C) daily.