Timeline of the 2004 Pacific hurricane season

The 2004 Pacific hurricane season consisted of the events that occurred in the annual cycle of tropical cyclone formation over the Pacific Ocean north of the equator and east of the International Date Line. The official bounds of each Pacific hurricane season are dates that conventionally delineate the period each year during which tropical cyclones tend to form in the basin according to the National Hurricane Center (NHC), beginning on May 15 in the Eastern Pacific proper (east of 140°W) and June 1 in the Central Pacific (140°W to the International Date Line), and ending on November 30 in both areas. However, tropical cyclogenesis is possible at any time of year. The first tropical cyclone of the season, Tropical Storm Agatha, developed on May 22; the final, Tropical Depression Sixteen-E, dissipated on October 26.

Activity during the 2004 season was below average. A total of seventeen tropical depressions formed, with twelve going on to become named tropical storms. Six storms became hurricanes, of which three further intensified into major hurricanes. Persisting throughout the season was an area of atmospheric and oceanic conditions hostile to tropical cyclones, including below-average sea surface temperatures and a stable air mass. A strong ridge over Mexico frequently steered systems toward this area, limiting their development. The season's general lack of activity was reflected by an overall Accumulated Cyclone Energy index of 71.1 units, which is the seventh-lowest value on record for a Pacific hurricane season as of December 2024.

Impacts on land were unusually light during the season, largely on account of the aforementioned ridge steering the vast majority of tropical cyclones out to sea. No systems caused any confirmed fatalities, although Hurricane Javier in September caused three fishermen to go missing off the coast of Oaxaca. Javier and Sixteen-E made landfall as tropical depressions in northwestern Mexico, where they caused minor flooding; Sixteen-E also generated locally strong winds and a possible tornado. The remnants of both systems produced heavy rainfall in portions of the western United States. Hurricane Howard in early September washed out roads in western portions of the Baja California peninsula and prompted water rescues in California due to high surf. In mid-October, Tropical Storm Lester caused rainfall of up to 5 in (130 mm) in southern Mexico when it passed close to the coast.

Prior to 2015, two time zones were utilized in the Eastern Pacific basin: Pacific east of 140°W, and Hawaii−Aleutian from 140°W to the International Date Line. For convenience, each event is listed in Coordinated Universal Time (UTC) first, using the 24-hour clock (where 00:00 = midnight UTC), with the respective local time included in parentheses. Figures for maximum sustained winds and position estimates are rounded to the nearest five units (knots, miles, or kilometers) and averaged over one minute, 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. This timeline documents the formation of tropical cyclones as well as the strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season. It also includes information that was not released while the storm was active, meaning that data from post-storm reviews by the National Hurricane Center and the Central Pacific Hurricane Center is included.