The Atlantic hurricane season officially begins in June, on June 1. The conventional season runs through November 30, covering the months when most tropical and subtropical cyclones form in the North Atlantic.
These dates are a calendar convention, not a physical limit. Tropical storms and hurricanes can develop outside the official season, and forecasters monitor the Atlantic year-round. The boundaries were chosen because they contain more than 97% of Atlantic tropical cyclone activity while giving the public and emergency planners an easy-to-remember period for heightened preparedness.
The season is most active later in the year, with activity typically peaking from late August through September. September 10 is the climatological midpoint of peak activity, when warm ocean water and other atmospheric conditions most often support tropical cyclone development.
A common mix-up is confusing the official season start with the start of routine outlooks. After several early-season storms, the National Hurricane Center began issuing its regular tropical weather outlooks on May 15 starting in 2021. That change did not alter the official June 1 season start. Likewise, an early storm is described as an off-season storm rather than evidence that the season began early.