Irma developed on August 30 near the Cape Verde Islands from a tropical wave that had shifted from the west coast of Africa two days earlier. Under favorable conditions, Irma intensified rapidly shortly after it formed, becoming a Category 2 hurricane just 24 hours after its formation. It became a major hurricane soon. However, the intensity began
to fluctuate over the following days due to eye formation.
On September 4, Irma became a Category 5 hurricane with winds of 175 mph (280 km / h), making it the Atlantic's strongest hurricane since Félix's 2007 season and breaking a record considered the hurricane stronger than the season, beating David of the 1979 season.