Even with more than one-third of the hurricane season left, 2017 is already earning a spot on the most active list. So far we've seen 13 named storms, 7 hurricanes, and 4 major hurricanes (category 3 or higher) . This is the first time that two category 4 hurricanes have made landfall in the Continental U.S. in the same season. According to Colorado State tropical meteorologist Dr. Phil Klotzbach, there have only been eight other years dating back to the mid 19th century that had generated seven or more hurricanes by September 17.
Another measuring tool meteorologists use to determine the activeness of a season is called the ACE index. ACE stands for accumulated cyclone energy, and the index is calculated by adding each named storms wind speed through its life. Using the ACE index, only 7 seasons have been more active through mid September than this year. Those seven seasons include 1893, 1926, 1933, 1950, 1995,2004, and 2005.
The financial costs this season have already surpassed the previous costliest season of 2005, with $143.5 billion in damages due to Katrina and three other hurricanes that year. Damages from Harvey and Irma have been estimated at around $290 billion. This number will continue to climb when damage from Hurricane Maria is factored in. The 2017 hurricane season runs through November 30th.