The season officially began on June 1, 2011, and ended on November 30, 2011, dates that conventionally delimit the period of each year when most tropical cyclones develop in the Atlantic basin.
Hurricane Irene was a powerful and unusually large storm that made several landfalls along the East Coast of the United States after peaking with maximum sustained winds of 120 mph (195 km/h).
This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season.
The time zones utilized (east to west) prior to 2020 were: Atlantic, Eastern, and Central.
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.