The 1939 California tropical storm, also known as the 1939 Long Beach tropical storm, and El Cordonazo (referring to the Cordonazo winds or the "Lash of St. Francis" (Spanish: el cordonazo de San Francisco)), was a tropical cyclone that affected Southern California in September 1939. Formerly classified a hurricane, it was the first tropical cyclone to directly affect California since the 1858 San Diego hurricane, and is the only tropical cyclone of tropical-storm strength (or greater) to make landfall in the U.S. state of California. The storm caused heavy flooding, leaving many dead, mostly at sea.

On September 15, a tropical depression formed off the southern coast of Central America. It moved west-northwestward, passing southwest of the Revillagigedo Islands. It then turned north and then northeastward. For some time, it was a hurricane, and it lost that intensity on or just before September 25. The tropical storm made landfall near San Pedro, California, early on September 25, with winds of severe gale strength. It dissipated later that day. The strongest reported sustained wind was of Force 11 strength, which was reported by a ship, making this system a minimal hurricane. The lowest pressure was reported by the same ship, and was at 28.67 inHg (971 mb).

Due to the rotation of the Earth, tropical cyclones in the Northern Hemisphere tend to move from east to west. This causes tropical cyclones to approach the West Coast of the United States infrequently. Another inhibiting factor for a California landfall is the surrounding water temperatures. Because of the water currents, the waters off the coast of California are rarely above 70 °F (21 °C), which is too cold for hurricanes to sustain themselves. This tropical cyclone was rare enough that only three other eastern Pacific tropical cyclones brought tropical storm-force winds to the Continental United States during the twentieth century. The Long Beach Tropical Storm was the only one to make landfall; the other three hit Mexico before moving north, but didn't make landfall in California.

The storm dropped heavy rain in California, with 5.66 inches (144 mm) falling in Los Angeles (5.24 inches or 133 millimetres in 24 hours) and 11.60 inches (295 mm) recorded at Mount Wilson, both September records. Over three hours, one thunderstorm dropped nearly 7 inches (180 mm) of rain on Indio. 9.65 inches (245 mm) fell on Raywood Flat, and 1.51 inches (38 mm) on Palm Springs. 4.83 inches (123 mm) fell on Pasadena, a September record at the time. At the Citrus Belt near Anaheim, at least 4.63 inches (118 mm) of rain fell. The 11.60 inches (295 mm) at Mount Wilson is one of California's highest rainfall amounts from a tropical cyclone, although at least one system has a higher point maximum. The rains caused a flood 2 to 4 feet (0.6 to 1.2 m) deep in the Coachella Valley with heavy rain immediately preceding the tropical storm dropping 6.45 inches (164 mm) the day before the storm hit. The Los Angeles River, which was usually low during September, became a raging torrent.

With heavy rain immediately preceding the tropical storm, flooding killed 45 in Southern California. At sea, 48 were killed. However, the National Hurricane Center only attributes 45 deaths to this system. Six people caught on beaches drowned during the storm. Most other deaths were at sea. Twenty-four died aboard a vessel called the Spray as it attempted to dock at Point Mugu. The two survivors, a man and a woman, swam ashore and then walked five miles (8 km) to Oxnard. Fifteen people from Ventura drowned aboard a fishing boat named Lur. Many other vessels were sunk, capsized, or blown ashore.

Many low-lying areas were flooded. The Hamilton Bowl overflowed, flooding the Signal Hill area. Along the shore from Malibu to Huntington Beach houses were flooded. Throughout the area, thousands of people were stranded in their homes. Streets in Los Angeles proper were covered with water, flooding buildings and stalling cars. Flooding in Inglewood and Los Angeles reached a depth of 2 to 3 feet (0.61 to 0.91 m). Construction on a flood control project in the Los Angeles River's channel by the Army Corps of Engineers was stopped by the flooding. Windows throughout Long Beach were smashed by the wind. At Belmont Shore and the Peninsula, waves undermined ten homes before washing them away. Debris was scattered throughout the coast. Agriculture was disrupted. Crop damage in the Coachella Valley reached 75%.

Rains washed away a 150-foot (46 m) section of the Southern Pacific Railroad near Indio, and a stretch of the Santa Fe main line near Needles. Waters backing up from a storm drain under construction in the San Gabriel Valley blocked California State Route 60. The pier at Point Mugu was washed away. In Pasadena, 5000 people were left without electricity and 2000 telephones lost service. Communications throughout the affected area was disrupted or rendered impossible. The total amount of damage was $2 million (1939 USD, $44 million in 2023 USD).

The tropical storm was credited with at least one beneficial effect: it ended a vicious heat wave that had lasted for over a week and killed at least 90 people.

People were caught unprepared by the storm, which was described as "sudden". Some people were still on the beach at Long Beach when the wind reached 40 mph (64 km/h; 35 kn), at which time lifeguards closed the beach. Schools were closed there. At sea, the Coast Guard and Navy conducted rescue operations, saving dozens of people. In response to Californians' unpreparedness, the Weather Bureau established a forecast office for southern California, which began operations in February 1940.

• List of California hurricanes
• List of wettest tropical cyclones in California
• Hurricane Linda (2015)- One of wettest Los Angeles rain was "2.39" inches, and remnants, but only behind 1939 was "3.96" inches.
• Hurricane Hilary – most recent tropical storm to impact California, only 2.48" inches in Los Angeles around August.

• USA Today Tropical Storm Info Archived 2009-02-26 at the Wayback Machine
• 10 most important California weather events
• More storm information
• An Overview of the Los Angeles Climate
• A history of Significant Local Weather Events