Tropical cyclone climatology

Global Tropical Storm Formation

Approximately 85 tropical storms annually develop over the world's warm tropical oceans.

Cyclone, Hurricane, and Typhoon Development

More than half (45) of these storms intensify into tropical cyclones, known regionally as hurricanes or typhoons.

Geographical Distribution

72% of these tropical storms form in the Northern Hemisphere. The remaining 28% develop in the Southern Hemisphere.

The diagram below illustrates the seasonal tropical cyclone activity across various basins.

Graphs depicting the average seasonal cycles of tropical cyclones in various ocean basins with peak activity typically occurring in late summer and early fall.

Average annual cycle of tropical cyclone occurrence for each ocean basin. The abscissa spans the 13 months, December through January of the following year; the ordinate is the number of storms per hundred years. For each day, the graph shows the number of years that a cyclone was present (normalized per 100 years). The blue line represents all tropical cyclones (surface winds greater than 17 m s-1 or 34 knots); shading represents tropical cyclones of hurricane strength (surface winds greater than 33 m s-1 or 64 knots).

NOAA/NWS/NHC