Since the reliable record keeping of tropical cyclone data within the North Atlantic Ocean began in 1851, there have been 1,505 systems of at least tropical storm intensity, and 879 of at least hurricane intensity. Though a majority of these tropical cyclones have fallen within climatological averages, prevailing atmospheric conditions occasionally lead to anomalous tropical systems, which at times reach extremes in statistical record-keeping, including in duration and intensity. The scope of this list is limited to tropical cyclone records solely within the Atlantic Ocean north of the equator and is subdivided by their reason for notability. Climatologically speaking, approximately 97 percent of tropical cyclones that form in the North Atlantic develop between the dates of June 1 and November 30 – dates which delimit the modern-day Atlantic hurricane season.
Though the beginning of the annual hurricane season has historically remained the same, the official end of the hurricane season has shifted from its initial date of October 31. Regardless, on average once every few years a tropical cyclone develops outside the outside the limit of the season. From 1851 to the present day, there have been 66 tropical cyclones in the off-season, with the most recent being Hurricane Alex in 2016. The first tropical cyclone of the 1938 North Atlantic hurricane season, which formed on January 3, became the earliest forming tropical storm and hurricane after reanalysis concluded on the storm in December 2012. In 1951, Hurricane Able became the earliest forming major hurricane – a tropical cyclone with winds exceeding 115 mph – after it reached the equivalent of Category 3 intensity on the Saffir-Simpson Hurricane Wind Scale on May 21. Though it developed within the bounds of the North Atlantic hurricane season, Hurricane Audrey in 1957 became the earliest developing Category 4 hurricane on record after it reached the intensity on June 27. The earliest-forming Category 5 hurricane, Emily, reached the highest intensity on the Saffir-Simpson Hurricane Wind Scale on July 17, 2005.
Though the official end of the Atlantic hurricane season occurs on November 30, the dates of October 31 and November 15 have also been historically marked as the official end date for the hurricane season. December, the only month of the year after the hurricane season, has featured the cyclogenesis of 15 tropical cyclones. Tropical Storm Zeta in 2005 and Hurricane Alex in January, 2016 were the latest tropical cyclones to attain tropical storm intensities as they did so on December 30 with regards to Zeta and January with regards to Hurricane Alex in 2016. However, the second Hurricane Alice in 1954 was the latest forming tropical cyclone to attain hurricane intensity. Both Zeta and Alice were the only two storms to exist in two calendar years – the former from 1954 to 1955, and the latter from 2005 to 2006. No storms have been recorded to exceed Category 1 hurricane intensity in December.
In 1999, Hurricane Lenny reached Category 4 intensity on November 17 as it took an unprecedented west to east track across the Caribbean; its intensity made it the latest developing Category 4 hurricane, though this was well within the bounds of the hurricane season. Hurricane Hattie (October 27-November 1, 1961) was initially thought to have been the latest forming Category 5 hurricane ever documented, though reanalysis indicated that a devastating hurricane in 1932 reached such intensity at a later date. Consequently, this made the hurricane the latest developing tropical cyclone to reach all four Saffir–Simpson Hurricane Wind Scale classifications past Category 1 intensity. The figures below show the zones of origin and tracks for different months during the hurricane season. These figures only depict average conditions. Hurricanes can originate in different locations and travel much different paths from the average. Nonetheless, having a sense of the general pattern can give you a better picture of the average hurricane season for your area.