The rare tropical storm that swamped Los Angeles in flooding rains
A sudden storm in Sept. 1939 caused major flooding across an area not accustomed to such rapid heavy rainfall
One of the few tropical storms on record to strike California came ashore near Los Angeles on Sept. 25, 1939.
The storm brought a tremendous amount of rain to a typically dry region of the world, unleashing major floods that killed dozens of people.
This tropical storm in 1939 remains the last time a storm officially made landfall in California.
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A prolific rainmaker
Folks across southern California likely believed that a brutal heat wave roasting the region in the middle of Sept. 1939 would be the worst weather that month. Temperatures in Los Angeles topped 38°C every day for an entire week, and readings down in San Diego reached 41.1°C on Sept. 21.
Nobody knew that a hurricane lurking off the western coast of Mexico would break that heat wave and cause its own set of problems throughout the region.
Moving along an unusual track, the unnamed storm spread heavy rain and high winds across southern California. The centre of the storm made landfall a few dozen kilometres south of Los Angeles as a high-end tropical storm.
Gusty winds downed trees and power lines throughout the region, claiming 48 lives when vessels sank or capsized at sea.
Drenching tropical rainfall caused most of the issues and damage. Heavy rain on arid, impermeable surfaces caused widespread flooding that reportedly killed an additional 45 people.
Los Angeles reported 143 mm of rain from the storm, most of which fell within 24 hours. The desert community of Palm Springs saw 43 mm of rain. These regions typically see very little to no rainfall during the summer season. Tropical moisture pushed far inland to bring 47 mm of precipitation to Las Vegas.
Tropical systems are rare in southern California
Alongside the 1939 tropical storm, only two other systems are known to have reached California intact, including the San Diego Hurricane of 1858 and Tropical Storm Nora in 1997. Nora made landfall in Mexico and tracked through southeastern California at tropical storm intensity.
Full-fledged tropical systems are a generational event in California for good reason. Upwelling off the U.S. West Coast keeps ocean waters here far too chilly to sustain the thunderstorms around the centre of a system.
Despite the relative rarity of a direct threat, interests in California always have to keep a close eye on tropical activity across the eastern Pacific. It’s common for the remnants of tropical systems moving northward to reach California.
Tropical Storm Hilary prompted the first-ever tropical storm warning for Los Angeles and San Diego in Aug. 2023. Though the storm didn’t reach the state as a tropical system, it brought high winds and flooding to the region.
A study published in 2026 warned that California faces an increased threat for flooding from the remnants of tropical systems as the climate changes.