The Everglaes are a subtropical wetland located in the southern portion of the U.S. state of Florida, comprising the southern half of a large watershed. The entire system begins in the vicinity of Orlando with the Kissimmee River. The Everglades includes the region that spans from Lake Okeechobee south to Florida Bay, as well as the interconnected ecosystems within the boundary. The Kissimmee River discharges into Lake Okeechobee, a vast shallow fresh water lake. Water leaving Lake Okeechobee in the wet season forms the Everglades, a slow-moving river 60 miles (97 km) wide and over 100 miles (160 km) long, flowing southward across a slightly angled limestone shelf to Florida Bay at the southern end of the state. It is such a unique convergence of land, water, and climate that the use of singular and plural to refer to the Everglades is appropriate. Characteristics of the climate of South Florida include annual wet and dry seasons, and the region has a history of recurring flooding and drought that has shaped the natural environment.