By Reginald Stanley. Posted August 19, 2023, 4:15 AM.

As Hurricane Hilary (currently predicted to downgrade to Tropical Storm strength as it impacts Southern California) makes its approach to the Baja California Peninsula and southwestern United States, we take a moment to reflect on the last time a tropical cyclone directly impacted the state - nearly 84 years ago.

Such events impacting Southern California are extremely rare. Coastal waters off the west coast of the United States - including Southern California - are considered too cold to sustain tropical cyclone activity and development. While Southern California is no stranger to tropical and subtropical remnants, a tropical cyclone reaching the state at tropical storm-intensity (or above) has only been observed twice before in California's recorded history - 1939 and 1858, however the 1858 event did not make landfall. In September 1939, a tropical storm (formerly a hurricane) made landfall near San Pedro and Long Beach, and shattered daily rainfall records all across Southern California - many of those records stand to this day. In Downtown Los Angeles, 5.66 inches fell in only 24 hours. In Mount Wilson, 11.60 inches was recorded in 24 hours - a September record for that location. A thunderstorm associated with the tropical storm dropped nearly 7 inches of rain on the desert town of Indio in just three hours.

The tropical storm's impacts were severe. Many streets and buildings in the Los Angeles area proper were flooded. The Los Angeles River, normally low or dry in September, had become a raging torrent. Winds of reportedly severe gale strength were reported in Long Beach, destroying windows throughout the city. Ten homes in Long Beach's Belmont Shore were washed away, with debris scattered along the coast. Railroad tracks near Indio and Needles were swept away. Point Mugu's pier was destroyed. Over 5,000 people were left without electricity in Pasadena, while communications in areas affected by the tropical storm were effectively paralyzed. Total damage from the storm totaled $2 million (1939 USD), or $42 million (2022 USD).

The tropical storm did, however, end a brutal heat wave that had strangled the region for over a week immediately prior to the storm - a heat wave that led to 90 deaths. The tropical storm led to 93 deaths - 48 of which were at sea, according to the National Hurricane Center. Residents described the tropical storm as "sudden" and had been unprepared for its arrival and impact. As a result of the poor preparation for the storm and its severe impact on the region, the Weather Bureau established an office in Southern California, beginning operations in February 1940.