Hurricane Sandy, the largest Atlantic hurricane in diameter on record, was a late-season tropical cyclone that affected Jamaica, Cuba, the Bahamas, Haiti, the Dominican Republic, and the eastern seaboard of the United States, reaching to the area south of the Great Lakes Region of the United States and Eastern Canada. The 18th tropical cyclone, 18th named storm, and 10th hurricane of the 2012 Atlantic hurricane season, Sandy developed from an elongated tropical wave in the western Caribbean Sea on October 22. It became a tropical depression, quickly strengthened, and was upgraded to a tropical storm six hours later. Sandy moved slowly northward toward the Greater Antilles and gradually strengthened.