Atlantic hurricane season ends on November 30. Hurricane Alex formed on January 12, 2016, as a Category 1 hurricane, more than a month after that date. Both facts are true, and the difference between them explains how the season dates work.
What are the official dates?
The Atlantic hurricane season runs from June 1 to November 30. The Eastern Pacific season, which matters for Mexico and the west coast of Central America, runs from May 15 to November 30.
The dates were finalized in 1965. They were chosen to cover more than 97% of Atlantic tropical cyclone activity, so they describe a window, not a wall. The Central Pacific season, which covers Hawaii, starts later, on June 1.
The end of the season does not stop the forecasts. The National Hurricane Center issues advisories for any tropical cyclone that exists, on any date.
Why the date seems to keep moving
The season itself has not moved since 1965. Earlier definitions were different. In 1935, the official season ran from June 15 to October 31. In 1915 the start shifted to June 1, and in 1917 the end moved to November 30. The 1965 dates then became the standard.
What moved recently is the start of forecasting. Since 2021, the National Hurricane Center issues routine tropical weather outlooks beginning on May 15 instead of June 1. The World Meteorological Organization recommended the change because storms kept forming before the season opened. From 2015 through 2021, at least one storm formed before June 1 in seven consecutive years.
The Atlantic hurricane season officially ends on November 30, and the National Hurricane Center has issued routine outlooks starting May 15 since 2021.
Storms outside the dates
A tropical cyclone forms out of season about once every few years, mostly in May or December, according to NOAA’s Hurricane Research Division. Several went well beyond that.
- Alex formed on January 12, 2016, and reached Category 1 hurricane strength.
- Zeta formed on December 30, 2005, crossed into 2006, and ended on January 7.
- Lili was a Category 1 hurricane from December 12 to 24, 1984.
- Epsilon lasted from November 29 to December 8, 2005, and reached Category 1 hurricane strength.
Why risk falls but does not disappear
By late November, ocean water is cooler and wind shear is stronger across the Atlantic, so fewer storms can form and keep their structure. From August through October, the Atlantic records 96% of its major hurricane days. That leaves a small share for the rest of the year.
A small share is still a real share. Hurricane Iota reached Category 5 intensity in November 2020, in the last weeks of the season.
Use the date as a planning aid
November 30 works for insurance, marina schedules, and supply planning. It does not tell you whether a storm is forming this week. For a coastline in the Gulf of Mexico or the Caribbean, check the forecast in December the same way as in September.
To see how the peak compares, read why September 10 is the peak of hurricane season . For how storms get their names, read how hurricanes get named .
RainViewer alerts users when a tropical storm forms nearby, timed to when the storm is expected to reach their location.
RainViewer
