September is the peak month for tropical cyclone activity in the Atlantic. During the satellite era starting in 1966, the Atlantic has averaged 3.6 tropical storms and 2.5 hurricanes during the month of September.
The graphic above shows the formation points of 478 tropical storms during the month of September from the National Hurricane Center’s (NHC) historical data set extending from 1851 to 2008. Note that developments can occur just about anywhere over the tropical and subtropical North Atlantic, the Caribbean Sea, and the Gulf of Mexico.
NHC records also show that the second deadliest United States hurricane on record, the Lake Okeechobee Hurricane of 1928, occurred in September; the costliest United States hurricane on record after adjusting for inflation, population and wealth, the Great Miami Hurricane of 1926, occurred in September; and the most intense United States hurricane on record, the Labor Day Hurricane of 1935, struck the Florida Keys in September.