 Putnam County is included in the Indianapolis-Carmel-Anderson, IN Metropolitan Statistical Area.According to the 2010 census, the county has a total area of , of which (or 99.55%) is land and (or 0.45%) is water.In recent years, average temperatures in Greencastle have ranged from a low of in January to a high of in July, although a record low of was recorded in January 1985 and a record high of was recorded in July 1954.