The 2004 Atlantic hurricane season was notable as one of the deadliest and most costly Atlantic hurricane seasons on record. It officially began on June 1, 2004 and ended on November 30, although storm activity continued into December. This timeline documents tropical cyclone formations, strengthening, weakening, landfalls, extratropical transitions, as well as dissipations. The timeline includes information which was not operationally released, meaning that information from post-storm reviews by the National Hurricane Center, such as information on a storm that was not operationally warned upon, has been included.