The Atlantic hurricane season, which affects Florida and the rest of the Atlantic Basin, is a defined six-month period when tropical or subtropical cyclones are most likely to form. This activity occurs in the North Atlantic Ocean, the Caribbean Sea, and the Gulf of Mexico. Knowing the official start and end dates is the first step in preparation for anyone living or traveling in the region. The season officially runs from June 1st to November 30th, a period established by meteorological agencies for monitoring and forecasting.
The Official Timeline: June 1st to November 30th
The official Atlantic hurricane season runs from June 1st to November 30th. This six-month window is designated by the National Oceanic and Atmospheric Administration (NOAA) and the National Hurricane Center (NHC). These dates were established because they encompass approximately 97% of all tropical cyclone activity in the Atlantic Basin.
The start and end dates are rooted in the typical annual cycle of oceanic and atmospheric conditions. As summer begins, sea surface temperatures (SSTs) gradually increase, supplying the heat energy necessary to fuel tropical systems. The June 1st start date marks when SSTs generally reach the 26.5 degrees Celsius (80 degrees Fahrenheit) threshold required for sustained tropical cyclone development.
By November 30th, the northern Atlantic waters begin to cool, and atmospheric patterns become less conducive to hurricane formation. This defined timeline provides a clear, consistent period for the NHC to issue routine tropical weather outlooks and for emergency management agencies to coordinate preparedness efforts. However, the risk is not evenly spread across all six months.
Climatological Peak Activity
The six-month season does not present a uniform threat, as historical data shows a distinct spike in activity during late summer and early fall. The climatological peak for the Atlantic hurricane season is centered around September 10th. Most intense hurricane activity (Category 3 or higher on the Saffir-Simpson Hurricane Wind Scale) occurs within an eight to ten-week window from mid-August through mid-October.
Several environmental factors converge during this time to create favorable conditions for storm development and intensification. Sea surface temperatures reach their maximum warmth, providing the greatest amount of fuel for tropical systems. Atmospheric conditions exhibit reduced vertical wind shear, which is the change in wind speed or direction with height. Low wind shear is required for a tropical cyclone to maintain its vertical structure and strengthen.
The African Easterly Jet (AEJ) plays a significant role during the peak months by steering waves off the coast of Africa across the Atlantic. These African Easterly Waves serve as the seed disturbances for many powerful storms, often called Cape Verde-type hurricanes, that track toward the Caribbean and the Gulf of Mexico. On average, less than 2% of intense hurricane activity occurs before August 1st, with about 95% happening between August and October.
Out-of-Season Storm Activity
While the June 1st to November 30th timeline captures the vast majority of tropical systems, tropical or subtropical cyclogenesis is possible year-round. Storms that form outside the official six-month window are considered “out-of-season” anomalies. These occurrences are relatively rare, accounting for approximately 3% of all Atlantic tropical activity.
Such early or late storms typically occur in May or December, the months immediately adjacent to the official season. These systems are often short-lived or classified as subtropical, possessing characteristics of both tropical and non-tropical storms. The environment is less conducive to sustained development because sea surface temperatures are still borderline, or the atmosphere exhibits higher levels of vertical wind shear.
Despite their low frequency, these out-of-season storms have prompted changes in monitoring practices. Beginning in 2021, the NHC started issuing routine tropical weather outlooks on May 15th, ahead of the official season start. This change acknowledges the potential for early development and provides a longer lead time for public awareness and preparations.