Timeline of the 1999 Atlantic hurricane season

The 1999 Atlantic hurricane season was an event in the annual tropical cyclone season in the north Atlantic Ocean. This Atlantic hurricane season saw a near-average number of named tropical storms, though five of them became dangerous hurricanes of Category 4 intensity on the 5-level Saffir–Simpson scale, the most in a single season since 1886. The season officially began on June 1, 1999 and ended on November 30, 1999. These dates, adopted by convention, historically describe the period in each year when most tropical systems form. This season's first storm, Tropical Storm Arlene, formed on June 11, while the last, Hurricane Lenny, dissipated on November 23.

Altogether, 12 tropical storms formed during the season, including eight hurricanes of which five intensified into major hurricanes. There were also four tropical depressions that did not reach tropical storm strength. The most significant hurricane of the season was Hurricane Floyd, which caused devastating flooding along the East Coast of the United States, especially in North Carolina, which had been hit only ten days earlier by Hurricane Dennis. Another strong hurricane, Hurricane Lenny became the strongest November Atlantic hurricane on record, and maintained a west-to-east track through the Caribbean for nearly its entire duration. Because of its unusual path, it developed the nickname "Wrong Way Lenny." The deadliest tropical cyclone of the season was Tropical Depression Eleven, whose heavy rain and resultant flooding caused 400 deaths in Mexico.

This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season. It includes information that was not released throughout the season, meaning that data from post-storm reviews by the National Hurricane Center, such as a storm that was not initially warned upon, has been included.

The time stamp for each event is first stated using Coordinated Universal Time (UTC), the 24-hour clock where 00:00 = midnight UTC. The NHC uses both UTC and the time zone where the center of the tropical cyclone is currently located. The time zones utilized (east to west) prior to 2020 were: Atlantic, Eastern, and Central. In this timeline, the respective area time is included in parentheses. Additionally, figures for maximum sustained winds and position estimates are rounded to the nearest 5 units (miles, or kilometers), following National Hurricane Center practice. Direct wind observations are rounded to the nearest whole number. Atmospheric pressures are listed to the nearest millibar and nearest hundredth of an inch of mercury.