[2] The drought-stricken Hawaiian Islands received beneficial rainfall from Hurricane Douglas in July and Tropical Storm Kenna in August.

The remnants of hurricanes Iselle, Marie, Norbert, and Odile all contributed to enhanced precipitation across the Southwestern United States during the season, including snowfall in higher elevations; flash flooding killed one person in Texas.

Strong westerly wind shear inhibited this disturbance initially, but atmospheric conditions improved over subsequent days,[3] allowing it to become the season's first tropical depression around 18:00 UTC on May 17.

After reaching peak winds of 75 mph (121 km/h), Boris weakened and began to move erratically as upper-level troughing progressed over western Mexico.

The cyclone weakened to a tropical storm on August 21, but it regained hurricane strength two days later before feeling the effects of an upper-level trough off Baja California.

The newly developed system moved west-northwest and intensified over warm waters,[3] becoming Tropical Storm Douglas by 18:00 UTC on June 25 and strengthening into a hurricane about 48 hours later.

It curved north and made landfall about 90 mi (140 km) northwest of Cabo San Lucas, Baja California Sur, at 09:00 UTC on July 14, possessing 35 mph (56 km/h) winds by that point.

[4] A potent upper-level trough dug southward into the coastal waters of California, creating a steering pattern that shunted the system northwest.

[4] An expansive upper-level outflow setup was disrupted by an increase in wind shear, which caused Julio to weaken despite warm ocean waters.

A nearby upper-level trough began to shear Keli, directing its convection to the north; low-level flow, meanwhile, forced the storm's actual center westward.

[4] On August 18, the cyclone crossed into the Central Pacific, attaining maximum winds of 60 mph (97 km/h) as estimated by a reconnaissance aircraft despite a generally disheveled presentation on satellite imagery.

[4] The remnants of the cyclone curved northwest and moved across the Big Island of Hawaii, producing rainfall accumulations of 6–8 in (150–200 mm) across its windward districts.

[4] Four days later, a reconnaissance aircraft intercepted the cyclone for the first time, finding winds of 50 mph (80 km/h) and supporting the system's upgrade to Tropical Storm Lala.

The system moved rapidly westward amid a favorable combination of low wind shear and warm ocean waters.

[11] While the lack of satellite coverage made tracking the system difficult,[5] forecasters believe it organized into Tropical Storm Moke by 06:00 UTC on September 4.

[4][5] As a tropical system, Moke produced wind gusts up to 35 mph (56 km/h) on Midway Island and slightly more severe conditions on Kure Atoll.

Floods inundated roads, including U.S. Route 95 in California, and frequent lightning caused power outages to dozen of homes.

[4] Embedded within weak steering flow, the newly named cyclone wound its way north, particularly after upper-level trough developed over the Rocky Mountains.

[4] On September 23, a reconnaissance aircraft intercepted Norbert and its well-defined eye, marking the first time that the inner core of a hurricane was mapped three-dimensionally.

[4] While the storm is officially recognized as dissipating over Baja California,[4] forecasters in Arizona expressed high confidence that it remained a tropical cyclone into that state.

[15] In the small fishing communities of Punta Abreojos and La Bocana along the coastline of Baja California Sur, 90 percent of structures were demolished.

[18] Slightly higher accumulations were reported in Arizona, where flash flood watches were hoisted across several counties and some school districts released students early owing to those concerns.

Those floods damaged countless structures, severely affected crops, left thousands of residents displaced, and killed many people.

[4] The cyclone curved northeast ahead of an upper-level trough over Baja California, and that feature brought Polo into colder waters and higher wind shear.

[4] Moisture from the remnants of the storm streamed north into the Southwestern United States, prompting flash flood watches across Utah, Arizona, New Mexico, and Texas.

It remained steady state for several days while moving west but ultimately organized into a tropical depression around 18:00 UTC on October 7.

The depression encountered warm waters along its track,[3] which fueled its organization into Tropical Storm Rachel by 06:00 UTC on October 9.

[4] Simon soon encountered increasingly cool waters and began to weaken,[3] dissipating over the open East Pacific after 00:00 UTC on November 8 and drawing the season to a close.

However, it was positioned on the south side of an upper-level trough extending from Texas into Mexico, and the shearing effects of that feature caused the cyclone to dissipate on September 22; its remnants continued inland about 50 mi (80 km) east of Salina Cruz.

In spite of very warm ocean waters, the system struggled under the influence of Hurricane Norbert to the west and the close proximity of the Sierra Madre del Sur.