2003 Pacific typhoon season

The 2003 Pacific typhoon season was a below-average annual cycle of tropical cyclogenesis in the northwestern Pacific Ocean, exhibiting the development of 45 tropical depressions, of which 21 became named storms; of those, 14 became typhoons. Though every month with the exception of February and March featured tropical activity, most storms developed from May through November. During the season, tropical cyclones affected the Philippines, Japan, China, the Korean Peninsula, Indochina, and various islands in the western Pacific.

The season ran year-round, with the first storm, Yanyan, developing west of the Marshall Islands on January 15. In April, Typhoon Kujira became one of the longest-lasting Pacific typhoons in history and attained climatological records for its unusually early impacts. Typhoon Imbudo in July killed 85 people when it struck the Philippines and China. It was followed soon after by Tropical Storm Koni, which hit the same countries as well as Vietnam. August was a highly active month for tropical cyclogenesis, with five named storms. In September, Typhoon Maemi became the strongest tropical cyclone of the season, with a minimum barometric pressure of 910 mbar (hPa; 26.87 inHg). Maemi later struck South Korea, becoming one of the country's costliest typhoons after causing US$4.8 billion in damage. In October, two typhoons – Ketsana and Parma – existed simultaneously while staying away from land In late November, Typhoon Lupit devastated areas of Yap State in the Federated States of Micronesia. The season closed with the dissipation of a tropical depression east of the Philippines on December 27.

The scope of this article is limited to the Pacific Ocean, north of the equator and west of the International Date Line. Storms that form east of the date line and north of the equator are called hurricanes; see 2003 Pacific hurricane season. Tropical storms formed in the entire northwest Pacific basin are assigned a name by the Tokyo Typhoon Center. Tropical depressions in this basin monitored by the Joint Typhoon Warning Center (JTWC) have the "W" suffix added to their number. Tropical depressions that enter or form in the Philippine area of responsibility are assigned a name by the Philippine Atmospheric, Geophysical and Astronomical Services Administration (PAGASA). This can often result in the same storm having two names.