The Strongest Hurricane Month Ever

September 2017 Strongest Hurricane Month in Recorded History

January 29, 2019
Hurricane Maria and Puerto Rico

Hurricane Maria approaches Puerto Rico


We all know this hurricane season has been active, but how active? September 2017 was the strongest hurricane month ever recorded. Here’s why.

First, know that September is typically the busiest month for North American Atlantic Hurricanes due to the conveyor belt of low-pressure systems moving off Africa’s west coast into the Atlantic reach its greatest strength. Additionally, the Atlantic is at its peak of heat and wind shear is normally low.


However, September 2017 crushed the previous record in September 2004. Hurricane strength is measured by ACE (accumulated cyclone energy). By adding each tropical storm or hurricane’s wind speed through its life cycle this past September stands at 175 units versus 155 during the same month in 2014. Consider that September 2017’s ACE included Irma, Jose, Katia, Lee and Maria. All of those except Katia were long-lived hurricanes, and Lee and Katia were the only ones to not reach Category 4 or Category 5 intensity at their peaks.

See 2017 hurricane names.


September 2017 also broke several cumulative day records. A hurricane day is defined as a measure of hurricane activity, one unit of which occurs as four 6-hour periods during which a tropical cyclone is observed or is estimated to have hurricane-force winds. This past month created the following cumulative day records.

  -Cumulative Days of named storms (53.5 days, beating the mark of 52.25 days in September 2004)

  -Cumulative Hurricane days (40.25 days, beating 34.5 in September, 1926)

  -Cumulative major hurricane days (18, beating 17.25 days in September, 1961)

While this hurricane season is not on pace to break 2005’s record for total named storms, there is still a quarter of the hurricane season left.


Already 2017 has nearly broken the record for hurricanes, and category three or higher hurricanes. It has been a busy season so far and it will be interesting to see what the remaining two months bring.

See the 2017 hurricane forecast.

About This Blog

Are you a weather watcher? Welcome to “Weather Whispers” by James Garriss and until recently, Evelyn Browning Garriss. With expertise and humor, this column covers everything weather—from weather forecasts to WHY extreme weather happens to ways that weather affects your life from farming to your grocery bill. Enjoy weather facts, folklore, and fun!

With heavy hearts, we share the news that historical climatologist and immensely entertaining Almanac contributor Evelyn Browning Garriss passed away in late June 2017. Evelyn shared her lifetime of weather knowledge with Almanac editors and readers, explaining weather phenomena in conversation and expounding on topics in articles for the print edition of The Old Farmer’s Almanac as well as in these articles. We were honored to know and work with her as her time allowed, which is to say when she was not giving lectures to, writing articles for, and consulting with scientists, academia, investors, and government agencies around the world. She will be greatly missed by the Almanac staff and readers.