The 2017 Atlantic hurricane season was an extremely active season; surpassing the activity of the 2005 season, thus making it the most active Atlantic hurricane season on record. It was extremely active due to a record-breaking La Niña in the Pacific, which produced record low wind shear across the Atlantic. In addition, the AMO was the most positive level on record, resulting in hot sea surface temperatures throughout the Atlantic. The season's activity also made it the costliest on record.