At a Glance
- Sept. 10 is the climatological peak of the Atlantic hurricane season.
- This is when conditions are most optimal for tropical storms and hurricanes over the largest area.
- It doesn't guarantee there will be a named storm active on Sept. 10, however.
Friday marks the statistical peak of the Atlantic hurricane season. It's when the Atlantic Basin has had the most hurricanes and named storms over the course of history.
This seasonal peak is also when conditions are most optimal for the development of tropical storms and hurricanes.
There's an overlap of favorable factors in early-mid September, including ocean water reaching its highest temperature, the atmosphere's ability to generate thunderstorms hitting its peak, and hostile shearing winds declining to a minimum. A parade of disturbances known as tropical waves, which act as seeds for development and peak in July, are still numerous in September.
These overlapping favorable factors occur over a larger area of the Atlantic Basin compared to early and late in the season. So there's more real estate open for tropical development during the seasonal peak.
All of those factors lead to more named storms and hurricanes during the statistical peak of hurricane season, as shown in the graph below.
The graph indicates the number of active named storms and hurricanes on each day of the Atlantic hurricane season in the historical record.
It clearly shows the three-month period from August through October encompasses the majority of named storms (77 percent) and hurricanes (87 percent) in an average season.
It also shows a distinct peak day with the most active named storms and hurricanes is Sept. 10.
Colorado State University tropical scientist Phil Klotzbach said that roughly three-quarters of Atlantic hurricane seasons since 1966 have had at least one active named storm on Sept. 10. Also, half of all seasons have had at least one active hurricane on this date.
This doesn't guarantee every Sept. 10 will have a rash of Atlantic named storms.
How Much of the Season is Left?
The 2021 season has already been an active one.
There have been 12 named storms so far this season, five of which became hurricanes. That includes six U.S. landfalls from named storms this season, including Claudette (formed over Louisiana), Danny, Elsa, Fred, Henri and Ida.
An average hurricane season would produce another five named storms, including three hurricanes, one of which would reach at least Category 3 intensity.
Of course, the most important statistic is how many of these named storms and hurricanes strike land.
Later in the season, development can occur closer to land in the western Caribbean Sea, southwest Atlantic Ocean and Gulf of Mexico. October 2018's devastating Category 5 Hurricane Michael was a stark recent example.
There's still a long way to go. In the past 10 years, the season's last storm fizzled as soon as Oct. 25 and as late as Dec. 7.
Now is the time to make sure you have a hurricane plan in case another storm threatens this season.
The Weather Company’s primary journalistic mission is to report on breaking weather news, the environment and the importance of science to our lives. This story does not necessarily represent the position of our parent company, IBM.