Hurricane Dolores was a powerful and moderately damaging tropical cyclone whose remnants brought record-breaking heavy rains and strong winds to California. The seventh named storm, fourth hurricane, and third major hurricane of the record-breaking 2015 Pacific hurricane season, Dolores formed from a tropical wave on July 11. The system gradually strengthened, attaining hurricane status on July 13. Dolores rapidly intensified as it neared the Baja California peninsula, finally peaking as a Category 4 hurricane on the Saffir–Simpson scale with winds of 130 mph (215 km/h) on July 15. An eyewall replacement cycle began and cooler sea-surface temperatures rapidly weakened the hurricane, and Dolores weakened to a tropical storm two days later. On July 18, Dolores degenerated into a remnant low west of the Baja California peninsula.

The 2015 Pacific hurricane season is the second-most active Pacific hurricane season on record, with 26 named storms, only behind the 1992 season. A record-tying 16 of those storms became hurricanes, and a record 11 storms further intensified into major hurricanes throughout the season. The Central Pacific, the portion of the Northeast Pacific Ocean between the International Date Line and the 140th meridian west, had its most active year on record, with 16 tropical cyclones forming in or entering the basin. Moreover, the season was the third-most active season in terms of accumulated cyclone energy, amassing a total of 290 units. The season officially started on May 15 in the Eastern Pacific and on June 1 in the Central Pacific; they both ended on November 30. These dates conventionally delimit the period of each year when most tropical cyclones form in the Northeast Pacific basin. However, the formation of tropical cyclones is possible at any time of the year. This was shown when a tropical depression formed on December 31. The above-average activity during the season was attributed in part to the very strong 2014–2016 El Niño event.