[nb 1][2] 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.

[2] 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).

This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season.

Additionally, figures for maximum sustained winds and position estimates are rounded to the nearest 5 units (knots, miles, or kilometers), following the convention used in the National Hurricane Center's products.