Timeline of the 2009 Atlantic hurricane season

The 2009 Atlantic hurricane season was an event in the annual tropical cyclone season in the North Atlantic Ocean. It was a below-average Atlantic hurricane season with nine named storms, the fewest since the 1997 season. The season officially began on June 1, 2009, and ended on November 30, 2009, dates that conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin. The first storm to form was Tropical Depression One on May 28, 2009 (one of three in 2009 that did not become a tropical storm), while the last storm, Hurricane Ida, dissipated on November 10.

Of the year's nine named storms, three became hurricanes with two intensifying further into major hurricanes. The inactivity throughout the basin was linked to the formation of an El Niño, which increased wind shear. The two most significant storms of the season, in terms of loss of life and damage, were Hurricanes Bill and Ida. Hurricane Bill was an unusually large storm and was also the season's strongest, attaining winds of 135 mph (215 km/h). Tropical Storm Claudette was the only storm in 2009 to make landfall in the United States; Hurricane Ida became extratropical shortly before coming ashore in Alabama.

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.