The October 2009 North American storm complex was a powerful extratropical cyclone that was associated with the remnants of Typhoon Melor, which brought extreme amounts of rainfall to California.

[7] Around the same time, an atmospheric river opened up (the Pineapple Express), channeling large amounts of moisture into the storm, resulting in heavy rainfall across California and other parts of the Western United States.

[8] Late on October 11, the extratropical cyclone absorbed the disorganized remnant of Typhoon Melor, causing the system's intensification to accelerate.

[11] Later on the same day, the storm complex reached a peak intensity of 966 millibars (28.5 inHg), even as the system began looping back northwestwards, towards the Gulf of Alaska.

[12] The two main lows merged again, even as the eastern chunk of moisture continued to accelerate eastward across the U.S., reaching the Central United States.

[13] On October 15, the eastern chunk of moisture began exiting the Northeastern United States, while the main system continued to move northwestward in the Gulf of Alaska, weakening into a 988 mbar storm.

[10] On October 17, the main low stalled just south of Alaska, while steadily weakening, even as the eastern chunk of moisture began a well-defined extratropical cyclone off the coast of Nova Scotia.

Hurricane Kathleen in 1976 held the record prior to Melor, producing a maximum of 14.76 in (375 mm) at San Gorgonio Mountain.

Although the rainfall was record-breaking, it significantly helped to alleviate one of California's worst droughts on record, spanning several years.

[21] Rainfall from the storm system also helped extinguish several wildfires that were burning in California at that time, including the large Station Fire.

A crash in the Caldecott Tunnel, requiring emergency repairs to the structure, led to a temporary closure and creating more traffic issues.

[22][27] Minor effects were recorded in terms of damage: one rockslide took place on Highway 101 and large swells affected the coastline.

At least 2 in (51 mm) of rain fell along the foothills of the mountains, making the remnants of Melor one of the wettest former tropical cyclones to impact the state of Nevada.

[31] Boston suburbs saw moderate, wet snow fall on the morning of October 16, in spots accumulating up to 0.5 inches (1.3 cm).