tropical storm arlene in april was the first storm of the season that formed on april 19. this was the third consecutive season in which storms form before the official start of the hurricane season. in late august, hurricane harvey became the first major hurricane to make landfall in the united states since wilma in 2005 and the first category 4 hurricane since charley in 2004. it also tied the record for the costliest tropical cyclone on record along with the most rainfall dropped by a tropical cyclone in the united states. in early september, hurricane irma became the first category 5 hurricane to impact the northern leeward islands on record. it later hit the florida keys as a category 4 hurricane. irma is the strongest hurricane ever recorded in the atlantic ocean outside of the gulf of mexico and caribbean sea. in late september, hurricane maria became the first category 5 hurricane to strike the island of dominica on record; and later it made landfall in puerto rico as a high-end category 4 hurricane. most of the deaths from this season occurred from maria, and caused a human crisis in puerto rico. in early october, hurricane nate became the fastest-moving hurricane in the gulf of mexico while also becoming the fourth hurricane of the year to make landfall in the contiguous united states. 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 ended with tropical storm rina, which became post-tropical on november 9.