According to the 2010 census, the county has a total area of 307.02 square miles (795.2 km2), of which 306.02 square miles (792.6 km2) (or 99.67%) is land and 1.01 square miles (2.6 km2) (or 0.33%) is water.
In recent years, average temperatures in Greenfield have ranged from a low of 17 °F (−8 °C) in January to a high of 85 °F (29 °C) in July, although a record low of −29 °F (−34 °C) was recorded in January 1985 and a record high of 103 °F (39 °C) was recorded in June 1988. Average monthly precipitation ranged from 2.37 inches (60 mm) in February to 4.85 inches (123 mm) in July.
County Council: The county council is the legislative branch of the county government and controls all the spending and revenue collection in the county. Representatives are elected from county districts. The council members serve four-year terms. They are responsible for setting salaries, the annual budget, and special spending. The council also has limited authority to impose local taxes, in the form of an income and property tax that is subject to state level approval, excise taxes, and service taxes.
Board of Commissioners: The executive body of the county is made of a board of commissioners. The commissioners are elected county-wide, in staggered terms, and each serves a four-year term. One of the commissioners, typically the most senior, serves as president. The commissioners are charged with executing the acts legislated by the council, collecting revenue, and managing the day-to-day functions of the county government.
Court: The county maintains a small claims court that can handle some civil cases. The judge on the court is elected to a term of four years and must be a member of the Indiana Bar Association. The judge is assisted by a constable who is also elected to a four-year term. In some cases, court decisions can be appealed to the state level circuit court.
County Officials: The county has several other elected offices, including sheriff, coroner, auditor, treasurer, recorder, surveyor, and circuit court clerk Each of these elected officers serves a term of four years and oversees a different part of county government. Members elected to county government positions are required to declare party affiliations and to be residents of the county.