Complex sentence: The season also featured the fastest tropical cyclone ever recorded in the Gulf of Mexico (Nate) and the first season to have four hurricanes make landfall in the United States or one of its territories (Harvey, Irma, Maria, and Nate) since 2005.
Split into simpler sentences: The season also featured the fastest tropical cyclone ever recorded in the Gulf of Mexico (Nate). The 2017 season is also the first season to have four hurricanes make landfall in the United States or one of its territories (Harvey, Irma, Maria, and Nate) since 2005.