Memphis is a city in the southwest corner of the U.S. state of Tennessee, and the county seat of Shelby County. Memphis rises above the Mississippi River on the 4th Chickasaw Bluff just south of the mouth of the Wolf River. Memphis has an estimated population of 669,651, making it the largest city in the state of Tennessee, the third largest in the Southeastern United States, and the 19th largest in the United States. Memphis has a humid subtropical climate, with four distinct seasons. Weather comes from elsewhere: winter weather comes from the upper Great Plains or from the Gulf of Mexico, leading to drastic swings. Summer weather may come from Texas (very hot and dry) or the Gulf (hot and humid.) The greater Memphis metropolitan area, including adjacent counties in Mississippi and Arkansas, has a population of 1,280,533. This makes Memphis the second largest metropolitan area in Tennessee, surpassed only by metropolitan Nashville, which overtook Memphis in recent years. Memphis is the youngest of Tennessee's four major cities (traditionally including Knoxville, Chattanooga, and Nashville). The Memphis region is known, particularly to media outlets, as the "Mid-South." The city's central location has led to much of its business development. Located on the Mississippi River and intersected by several freight railroads and two Interstate highways, Memphis is ideally located for commerce among the transportation and shipping industry.