1878 Atlantic hurricane season

The 1878 Atlantic hurricane season featured twelve known tropical cyclones, tied with 1886 and 1893 for the second-most active season in the latter half of the 19th century. Of the twelve tropical storms, eight strengthened into hurricanes, while two of those intensified into major hurricanes. However, in the absence of modern satellite and other remote-sensing technologies, only storms that affected populated land areas or encountered ships at sea were recorded, so the actual total could be higher. An undercount bias of zero to six tropical cyclones per year between 1851 and 1885 and zero to four per year between 1886 and 1910 has been estimated.

Of the known 1878 cyclones, both the third and fourth systems were first documented in 1995 by meteorologists José Fernández-Partagás and Henry F. Díaz, who also proposed large changes to the known tracks of the second, seventh, and eighth storms. Further analysis in the early 21st century by the Atlantic hurricane reanalysis project extended the duration of the third system by one day and identified major track changes for the fifth system. However, climate researcher Michael Chenoweth authored a reanalysis study, published in 2014, which concluded that the 1878 season featured a total of seventeen tropical cyclones, with the addition of five undocumented or previously excluded systems from the official hurricane database (HURDAT). Chenoweth also proposed some alterations to the track and intensity of each existing storm. However, these changes have yet to be incorporated into HURDAT.

Seasonal activity began by July 1, when stormy conditions associated with the first system started to impact Florida. All three known cyclones in August intensified into hurricanes and impacted land. Another three systems formed in September and each of them also strengthened into a hurricane. The last of the three, the seventh overall, became the most intense cyclone of the season, peaking as a Category 4 hurricane on the present-day Saffir–Simpson scale. Prior to this, the storm struck Haiti, leading to an unknown number of deaths when a brigantine capsized. Earlier in September, the fifth cyclone inflicted more than $919,000 (1878 USD) throughout its path and killed at least 60 people, with the dead rumored in the hundreds across the Caribbean, particularly in Haiti. In mid-October, the season's eighth storm drowned 27 people offshore New England. Later that month, the eleventh cyclone, the Gale of 1878, rendered substantial storm surge and wind damage throughout the Eastern United States, with 71 deaths and more than $2.46 million in damage. A record-tying five hurricanes existed in the month of October. The twelfth and final known system, which drowned three people in Puerto Rico, was last noted south of Jamaica on December 2.