| Basin: | EPac |
| Year: | 1931 |
| First Storm Formed: | July 3, 1931 |
| Last Storm Dissipated: | September 26, 1931 |
| Strongest Storm Name: | Five |
| Strongest Storm Pressure: | 976 |
| Total Storms: | 9 |
| Fatalities: | >150 |
| Damages: | 0.5 |
| Five Seasons: | 1929, 1930, 1931, 1932, 1933 |
| Atlantic Season: | 1931 Atlantic hurricane season |
| West Pacific Season: | 1931 Pacific typhoon season |
| North Indian Season: | 1930s North Indian Ocean cyclone seasons |
The 1931 Pacific hurricane season ran through the summer and fall of 1931. Before the satellite age started in the 1960s, data on east Pacific hurricanes was extremely unreliable. Most east Pacific storms were of no threat to land.
On July 3, a tropical cyclone possibly existed south of Acapulco. A ship measured a pressure of 29.55inHg.[1]
In the western part of the Gulf of Tehuantepec, a possible tropical cyclone existed on July 10. A ship reported a pressure of 29.66inHg.[1]
On July 21, a tropical cyclone began forming southwest of Manzanillo. It had completely formed by July 23. It moved along the coast, and entered the Gulf of California. It was last observed on July 25. This cyclone produced gales, and the lowest reported pressure was 29.39inHg.[1]
On July 26, a tropical cyclone existed midway between Acapulco and Salina Cruz. The lowest pressure reported by a ship was 29.63inHg.[1]
In the central Pacific east-southeast of the Hawaiian Islands, a ship encountered a tropical cyclone on August 30 and 31. It produced gales, and a pressure of 28.82inHg.[2]
South of the coast of Mexico, a tropical cyclone formed on September 6. It paralleled the coast, entered the Gulf of California, and dissipated by September 14.[3]
This system sank an American steamship called the Colombia (losses unknown).[3] On land, the area around Santa Rosalía, Baja California Sur was severely devastated. More than 100 people were killed on land,[4] mostly due to drowning.[5]
In Santa Rosalía itself, fifty were killed. Numerous small craft were sunk, with at least eight people going down with them. A merchant ship called Perkins was damaged in the storm, with two people washed overboard. On land, connections with the El Boleo copper mine were destroyed, with the mine itself flooded, causing $500,000 (1931 USD) in damage.[6] Hundreds were left homeless. In the aftermath, there was a shortage of food and medicine,[5] and troops were dispatched to maintain order.[6]
The next tropical cyclone was a slightly weaker and faster-moving clone of the previous one. On September 14, it formed at around the same location as the first, and took a similar path. It dissipated September 18 in the Gulf of California.[3]
A tropical cyclone existed from September 20 to on or just after September 24. It formed well south of the Mexican coast. It moved northwestward, and dissipated off the coast of the Baja California Peninsula.[3]
On September 26, a tropical cyclone formed south of the Mexican coast. It moved generally northwards, and dissipated in the Gulf of California sometime after September 29.[3]