Hurricane Irma was an extremely powerful and devastating tropical cyclone that caused extensive damage and loss of life across the Antilles and Eastern United States in September 2017. Irma was the first Category 5 hurricane to strike the Leeward Islands on record, though it was followed by Hurricane Maria, which struck the region at Category 5 intensity as well two weeks later. At the time, Irma was considered the most powerful hurricane on record in the open Atlantic region, outside of the Caribbean Sea and Gulf of Mexico, until it was surpassed by Hurricane Dorian two years later. It was also the third-strongest Atlantic hurricane at landfall ever recorded, just behind the 1935 Labor Day hurricane, Hurricane Melissa, and Dorian.
The ninth named storm, fourth hurricane, second major hurricane, and first Category 5 hurricane of the extremely active 2017 Atlantic hurricane season, Irma developed from a tropical wave near the Cape Verde Islands on August 30. Favorable conditions allowed Irma to rapidly intensify into a Category 3 hurricane on the Saffir–Simpson wind scale by late on August 31. The storm's intensity fluctuated between Categories 2 and 3 for the next several days, due to a series of eyewall replacement cycles. On September 4, Irma resumed intensifying, becoming a Category 5 hurricane by early on the next day. Early on September 6, Irma peaked with 1-minute sustained winds of 180 mph (290 km/h) and a minimum pressure of 914 hPa (27.0 inHg). Irma was the second-most intense tropical cyclone worldwide in 2017 in terms of barometric pressure, and the strongest worldwide in 2017 in terms of wind speed. Another eyewall replacement cycle caused Irma to weaken back to a Category 4 hurricane, but the storm re-attained Category 5 status before making landfall in Cuba. Although Irma briefly weakened to a Category 2 storm while making landfall on Cuba, the system re-intensified to Category 4 status as it crossed the warm waters of the Straits of Florida, before making landfall on Cudjoe Key on September 10. Irma then weakened to Category 3 status, prior to another landfall in Florida on Marco Island later that day. The system degraded into a remnant low over Alabama and ultimately dissipated on September 13 over Missouri.