The 1998 Pacific hurricane season was a moderately active Pacific hurricane season, featuring six major hurricanes. The season officially started on May 15 in the eastern Pacific and on June 1 in the central Pacific, and ended on November 30; these dates conventionally delimit the period during which most tropical cyclones form in that region. The first tropical cyclone developed on June 11, about ten days later than the normal start of the season. The final storm of the year, Hurricane Madeline, dissipated on October 20. Storm activity in the Central Pacific Hurricane Center's warning zone was low, with just one tropical depression observed in the region. Two tropical cyclones from the eastern Pacific (Darby and Estelle) also entered the central Pacific; the former did so as a hurricane.

The season produced 13 named storms, slightly below the average of 15 named storms per season. However, the season total of nine hurricanes was one above the average, and the total of six major hurricanes surpassed the average of three. Activity during the season was hindered by the northward movement of the Intertropical Convergence Zone (ITCZ). The ITCZ, which is normally situated south of the Gulf of Tehuantepec, shifted northward into Central and Southern Mexico, making the cyclone closer to cooler sea surface temperatures, hence limiting the number of storms that formed during the season. Although a semi-permanent anticyclone persisted through the summer of 1998, causing most of the storms to remain at sea, some storm did threaten the Baja California Peninsula due to a weakness in the anticyclone. Except for Hurricane Kay, all of the storms of the season originated from tropical waves.

The most notable tropical cyclone of the year was Hurricane Isis, which killed fourteen people when it made landfall on southern Baja California Sur and coastal Sinaloa in Mexico. Isis caused considerable damage in the nation while destroying more than 700 homes and damaging dozens of cars. It later produced sporadic rainfall in the southwestern United States, leading to some traffic accidents. In addition to Isis, Tropical Storm Javier moved ashore the coast of Jalisco in Mexico; the nation experienced indirect effects from four other storms, all of which remained offshore. One tropical cyclone, Hurricane Lester, affected Central America, causing two deaths in Guatemala. Three tropical cyclones brought light to moderate rainfall to the southwestern United States, and one hurricane produced rough surf along the coast of California. Hurricane Madeline contributed to a deadly and costly flood in southern Texas.