The 2018 Pacific hurricane season was an event in the annual cycle of tropical cyclone formation, in which tropical cyclones form in the eastern Pacific Ocean. The season officially started on May 15 in the eastern Pacific—east of 140°W—and began on June 1 in the central Pacific—the region between the International Date Line and 140°W, and ended on November 30. These dates typically cover the period of each year when most tropical cyclones form in the eastern Pacific basin. The season began with the formation of Tropical Depression One-E, which developed on May 10, and ended with the dissipation of the season's final storm, Tropical Storm Xavier, which dissipated as a tropical cyclone on November 5.
The 2018 hurricane season was exceptionally active and featured the highest Accumulated Cyclone Energy since reliable records began in 1971. Throughout the season, 26 tropical depressions developed, 23 of which became tropical storms. A total of 13 tropical storms reached hurricane strength, and 10 hurricanes achieved major hurricane intensity. The basin saw above-average activity across all regions from the International Date Line to the west coast of Mexico and Central America. Activity peaked from early August to early October, with several long-lived and powerful hurricanes developing in that time period. Several storms severely affected land, such as Hurricane Lane in Hawaii and Hurricane Willa in Mexico. In contrast to the similarly active 2015 Pacific hurricane season, 2018 was not significantly influenced by the El Niño–Southern Oscillation. Instead, low pressures and increased sea surface temperatures associated with the Pacific Meridional Mode supported the development of these intense and long-lived storms.
Four time zones are utilized in the basin: Central for storms east of 106°W, Mountain between 114.9°W and 106°W, Pacific between 140°W and 115°W, and Hawaii–Aleutian for storms between the International Date Line and 140°W. However, for convenience, all information is listed in Coordinated Universal Time (UTC) first with the respective local time included in parentheses. This timeline includes information that was not released while the storm was active, meaning that data from post-storm reviews by the National Hurricane Center is included. This timeline documents the formation of tropical cyclones as well as the strengthening, weakening, landfalls, extratropical transitions, and dissipations during the season.
Timeline of events
May
May 10
12:00 UTC (5:00 a.m. PDT) at – Tropical Depression One-E forms from an area of low pressure roughly southwest of Cabo San Lázaro, Baja California Sur. At the time, this was the second-earliest formation of a tropical cyclone in the Eastern Pacific proper behind Tropical Storm Adrian a year prior. 18:00 UTC (11:00 a.m. PDT) at – Tropical Depression One-E reaches its peak intensity with maximum sustained winds of 35 mph (55 km/h) and a minimum pressure of , approximately southwest of Cabo San Lázaro, Baja California Sur.
May 11
18:00 UTC (11:00 a.m. PDT) at – Tropical Depression One-E degenerates into a remnant low roughly west-southwest of Cabo San Lázaro, Baja California Sur.
May 15
The 2018 Eastern Pacific hurricane season officially begins.
June
June 1
The 2018 Central Pacific hurricane season officially begins.
June 6
00:00 UTC (7:00 p.m. CDT, June 5) at – Tropical Depression Two-E develops from an area of low pressure roughly south-southwest of Punta San Telmo, Michoacán. 06:00 UTC (12:00 a.m. MDT) at – Tropical Depression Two-E intensifies into Tropical Storm Aletta roughly south-southwest of Punta San Telmo, Michoacán.
June 7
18:00 UTC (12:00 p.m. MDT) at – Tropical Storm Aletta intensifies into a Category 1 hurricane roughly southwest of Punta Pérula, Jalisco.
June 8
00:00 UTC (6:00 p.m. MDT, June 7) at – Hurricane Aletta intensifies into a Category 2 hurricane roughly southwest of Punta Pérula, Jalisco. 06:00 UTC (12:00 a.m. MDT) at – Hurricane Aletta rapidly intensifies into a Category 3 hurricane about roughly southwest of Punta Pérula, Jalisco. 12:00 UTC (6:00 a.m. MDT) at – Hurricane Aletta quickly strengthens into a Category 4 hurricane roughly southwest of Punta Pérula, Jalisco. Simultaneously, the storm reaches peak intensity with winds of 140 mph (220 km/h) and a minimum pressure of .