The 2017 Atlantic hurricane season was a devastating and extremely active Atlantic hurricane season that became the costliest tropical cyclone season on record worldwide, with a damage total of at least $294.92 billion (USD). It was the second consecutive above–average season dating back to 2016. The season featured 17 named storms, 10 hurricanes, and 6 major hurricanes. Most of the season's damage was due to hurricanes Harvey, Irma, and Maria. Another notable hurricane, Nate, was the worst natural disaster in Costa Rican history. These four storm names were retired following the season due to the number of deaths and amount of damage they caused. Collectively, the tropical cyclones were responsible for at least 3,364 deaths. The season also had one of the highest accumulated cyclone energy (ACE) on record, with an index of 225 units. A record three hurricanes generated an ACE of over 40: Irma, Jose, and Maria. This season featured two Category 5 hurricanes, and the only season other than 2007 with two hurricanes making landfall at that intensity. The season's ten hurricanes occurred one after the other, the greatest number of consecutive hurricanes in the satellite era, and tied for the highest number of consecutive hurricanes ever observed in the Atlantic basin.
The season officially began on June 1 and ended on November 30. These dates historically describe the period of year when most tropical cyclones form in the Atlantic basin and are adopted by convention. However, as shown by Tropical Storm Arlene in April, the formation of tropical cyclones was possible at other times of the year. In late August, Hurricane Harvey struck Texas and became 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 United States and was the strongest since Charley in 2004. With damages estimated at $125 billion, the storm sequentially tied Hurricane Katrina for the costliest tropical cyclone on record and broke the record for most rainfall dropped by a tropical cyclone in the United States, with extreme flooding in the Houston area. In early September, Hurricane Irma became the first Category 5 hurricane to impact the northern Leeward Islands on record, later making landfall in the Florida Keys as a Category 4 hurricane. In terms of sustained winds, Irma, at the time, became the strongest hurricane ever recorded in the Atlantic basin outside of the Gulf of Mexico and Caribbean, with maximum sustained winds of 180 mph (285 km/h); it was later surpassed in 2019 by Hurricane Dorian. In mid September, Hurricane Maria became the first Category 5 hurricane in history to strike the island of Dominica. It later made landfall in Puerto Rico as a high-end Category 4 hurricane with catastrophic effect. Most of the deaths from this season occurred from Maria. In early October, Hurricane Nate became the fastest-moving tropical cyclone in the Gulf of Mexico on record and the third hurricane to strike the contiguous United States in 2017. Slightly over a week later, Hurricane Ophelia became the easternmost major hurricane in the Atlantic basin on record, and later impacted most of northern Europe as an extratropical cyclone. The season concluded with Tropical Storm Rina, which became extratropical on November 9.