Hurricane Harvey was a devastating Category 4 hurricane that made landfall on Texas and Louisiana in August 2017, causing catastrophic flooding and more than 100 deaths. It is tied with 2005's Hurricane Katrina as the costliest tropical cyclone on record, inflicting $125 billion in damage, primarily from catastrophic rainfall-triggered flooding in the Houston metropolitan area and Southeast Texas; this made the storm the costliest natural disaster recorded in Texas at the time. It was the first major hurricane to make landfall in the United States since Wilma in 2005, ending a record 12-year span in which no hurricanes made landfall at the intensity of a major hurricane throughout the country. In a four-day period, many areas received more than 40 inches (1,000 mm) of rain as the system slowly meandered over eastern Texas and adjacent waters, causing unprecedented flooding. With peak accumulations of 60.58 in (1,539 mm), in Nederland, Texas, Harvey was the wettest tropical cyclone on record in the United States. The resulting floods inundated hundreds of thousands of homes, which displaced more than 30,000 people and prompted more than 17,000 rescues.

The Saffir–Simpson hurricane wind scale (SSHWS) classifies hurricanes—which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms—into five categories distinguished by the intensities of their sustained winds. This measuring system was formerly known as the Saffir–Simpson hurricane scale, or SSHS.