List of off-season Atlantic hurricanes

In 1938, the United States Weather Bureau began issuing tropical cyclone warnings as a collaborative observation network for cities along the U.S. coastline, and the season was defined between June 15 and November 15.[2] In 1964, the season was extended to begin on June 1 and end on November 30,[3] which remains the official length of the season. About 97% of all tropical cyclones form within this time span, and activity usually peaks between August and October.[4] After Tropical Storm Ana formed in May 2015, former American Meteorological Society president Marshall Shepherd used Twitter to question whether the season should begin earlier. James Franklin of the National Hurricane Center believed there was little advantage to changing it because of the rarity of off-season storms, noting that May storms only formed on average once every six years since the advent of satellite imagery. Franklin opined that the season could begin on May 15 with little difficulty, coinciding with the beginning of the Pacific hurricane season, but an earlier start would be costlier and interfere with off-season work.[5]

Tropical cyclones have been named in the Atlantic since the 1947 Atlantic hurricane season, and subtropical cyclones have been recognized in HURDAT since 1968. The National Hurricane Center issues names for tropical and subtropical cyclones once their winds reach 39 mph (63 km/h). Before 1950, storms were numbered based on their appearance in the Atlantic hurricane database; tropical depressions were unnumbered.[6][7][8] Storms before 1851 are unofficial and are not part of the official Atlantic hurricane best track.[9] In addition, a hurricane from May 1863, labeled "Amanda", is included after being rediscovered in 2013.[10]

The wind speeds listed are maximum one-minute average sustained winds, and the pressure is the minimum barometric pressure; tropical cyclones listed with N/A under pressure indicates there is no known estimated pressure. For deaths, "None" indicates that there were no reports of fatalities; death tolls listed as "several" mean there were fatalities reported, but an exact total is unavailable. For both deaths and damage, N/A refers to no known total, although such storms may have impacted land. The damage totals are the United States dollar of the year of the storm.

Tropical Storm Odette in the Caribbean Sea in December 2003

In the official Atlantic hurricane database, which dates back to 1851, the first storm to occur outside of the current season was in 1865 in the Caribbean Sea. In the database, 87 tropical or subtropical cyclones have existed between December and May, most recently Tropical Storm Bertha in 2020.[6][7] In addition, there were at least five storms in May and another in December before the start of the official database.[9]

Storms were most likely to occur in May, followed by December. Out of all recorded storms in the database, only one cyclone was reported in the month of March; the 1908 March hurricane, as well as one tropical storm in February, which was the 1952 Groundhog Day Storm. In addition, only three tropical or subtropical cyclones formed in April – a subtropical storm in 1992, Tropical Storm Ana of 2003, and Tropical Storm Arlene of 2017. A hurricane in 1938, a tropical storm in 1951, a subtropical storm in 1978, and Hurricane Alex of 2016 occurred in January. Of all cyclones during the off-season, Hurricane Lili in 1984 lasted the longest, for a total of 12 days. Hurricane Epsilon, which formed in November, maintained hurricane status for five days in December 2005, longer than any other storm in December; the previous record was two and a half days, set by Hurricane Lili in 1984. Additionally, Hurricane Alice in 1954–1955 and Tropical Storm Zeta in 2005–2006 were the only recorded cyclones to have spanned two calendar years.[6][7]

Of the off-season storms that struck land, portions of the Caribbean were affected most.[6][7] Hurricane Alice was the only of the cyclones to strike land as a hurricane, doing so to islands in the northern Lesser Antilles; it caused locally heavy rainfall and moderate damage.[25] No hurricanes have ever made landfall in the United States during December, although at one point a storm in 1925 was believed to have done this.[6][61] One century earlier, a hurricane formed in the western Caribbean and struck Florida on or before June 3,[62] which was the earliest date for a United States hurricane landfall.[63] However, there is an unofficial hurricane in 1863 that struck the Florida panhandle, killing 110 people.[10] The deadliest official off-season storm was a tropical storm in May 1948, which killed 80 people in the Dominican Republic.[12]

The year with the most off-season storms was 1887, with a total of five existing in the off-season. The 1951 season had four, one of which a depression. Several others had three tropical cyclones, of which only 2003 had three tropical storms. The 1908 and 1951 seasons were the only ones with two hurricanes forming in the off-season. In seven seasons, there were storms both prior to the start of the season as well as after the season ended, those being 1887, 1911, 1951, 1953, 1954, 2003, and 2007; all but 1911 had tropical cyclones of at least tropical storm status before and after the season.[6][7] The most consecutive years to feature at least one pre-season storm was 6, between 2015 and 2020.

• List of off-season Australian region tropical cyclones
• List of off-season Pacific hurricanes
• List of off-season South Pacific tropical cyclones

• Atlantic hurricane database (HURDAT)