The 1915 Galveston hurricane was a tropical cyclone that caused extensive damage in the Galveston area in August 1915. Widespread damage was also documented throughout its path across the Caribbean Sea and the interior of the United States. Due to similarities in strength and trajectory, the storm drew comparisons with the deadly 1900 Galveston hurricane. While the newly completed Galveston Seawall mitigated a similar-scale disaster for Galveston, numerous fatalities occurred along unprotected stretches of the Texas coast due to the storm's 16.2 ft (4.9 m) storm surge. Overall, the major hurricane inflicted at least $30 million in damage (equivalent to $955 million in 2025) and killed 403–405 people. A demographic normalization of landfalling storms suggested that an equivalent storm in 2005 would cause $68.0 billion in damage in the United States.
Reanalyses of the Atlantic hurricane database concluded the storm formed near Cabo Verde on August 5, gradually strengthening into a hurricane as it tracked westward. However, it remained undetected by the United States Weather Bureau until it passed over the Lesser Antilles as a hurricane on August 10. The storm inflicted damage to shipping on the islands and flooded docks and streets in Martinique and Dominica. Two days later, the intensifying storm passed north of Jamaica, bringing 80–90 mph (130–140 km/h) winds to the northern coast. Significant losses were reported to the island's banana, beet, and sugar plantations, while coastal surge washed out roads and destroyed wharves; fifteen people in Jamaica were killed. Most houses and coconut trees were destroyed on Cayman Brac west of Jamaica, and substantial damage occurred across the Cayman Islands. On August 14, the hurricane clipped the western extremity of Cuba, killing fourteen. The storm's winds were estimated at 145 mph (230 km/h)—a Category 4 hurricane on the modern-day Saffir–Simpson hurricane wind scale; this was ultimately the hurricane's peak intensity.
Over the Gulf of Mexico, the hurricane caused 101 deaths, mostly from the sinking of the steamer Marowjine in the Yucatán Channel. During the early morning hours of August 17, the hurricane made landfall with winds of 130 mph (210 km/h) at San Luis Pass, Texas, approximately 26 mi (42 km) southwest of Galveston. Much of coastal Texas was affected by the storm's rough surf, with a total death toll of 275. Cities along Galveston Bay were inundated by storm surge, destroying entire towns and damaging numerous buildings. Galveston was largely protected by its seawall, but the strong waves caused extensive beach erosion that undermined 200 outlying homes. Ninety percent of homes outside the protection of the seawall on Galveston Island were destroyed. Most buildings in Houston were impacted, incurring $1 million in damage. The storm brought strong winds and torrential rainfall across East Texas, causing widespread cotton losses and damage to infrastructure—the highest rainfall total from the storm was 19.83 in (504 mm) in San Augustine, Texas.
The hurricane weakened as it tracked farther inland, degenerating into a tropical storm within a day of its landfall in Texas. A northeast curve soon followed, resulting in a track into the Ozarks and Ohio River Valley; the storm transitioned into an extratropical cyclone on August 20 over the Ozarks and dissipated over the Gulf of Saint Lawrence three days later. Heavy rainfall and significant river flooding occurred along the storm's path during this latter phase of its evolution. Levee breaches in along the White River in Arkansas and the Mississippi River in Illinois flooded entire towns. St. Louis, Missouri, recorded its rainiest 24-hour period in history, experiencing a deadly flood of the River Des Peres and Meramec River that impacted much of the city and surrounding suburbs, killing 20 people and destroying over a thousand homes.
On August 5, 1915, observations from Cabo Verde and the marine vicinity suggested the presence of a nearby tropical depression. On this basis, a 2008 reanalysis of the official hurricane database concluded that the depression formed by 12:00 UTC that day. Tracking west, the system gradually strengthened over the tropical Atlantic, attaining tropical storm intensity on August 6 and eventually reaching hurricane intensity three days later while well east of the Lesser Antilles. Despite the storm's power, the United States Weather Bureau was unaware of its existence for at least five days due to the sparsity of data over the open ocean; in a summary of the storm published in the Monthly Weather Review the following month, the Bureau noted that "there was nothing to indicate that conditions were favorable for the formation of a tropical storm, nor [...] was there anything pronounced to indicate its direction of progression ..." More conclusive evidence from weather observations in the Windward Islands allowed the Weather Bureau to begin monitoring the hurricane and disseminating warnings on the morning of August 10; at the time, the hurricane was situated roughly between Barbados and Dominica. The storm crossed into the Caribbean Sea the following day, passing south of St. Croix with growing intensity as indicated by rapidly falling pressures throughout the region.
Between August 12–13, the intensifying hurricane traversed the Caribbean Sea between Haiti and Jamaica with a bearing slightly north of west. Shortly after passing Jamaica, the storm became a major hurricane on the morning of August 13. On August 14, the storm moved near Cuba's Isle of Pines and across the Guanahacabibes Peninsula as a Category 4 hurricane with sustained winds of 145 mph (230 km/h). This was ultimately the storm's peak intensity as it weakened slightly once over the south-central Gulf of Mexico, though the storm still maintained Category 4 strength. At 07:00 UTC on August 17—in the early morning hours—the hurricane made landfall near San Luis Pass, approximately 26 mi (42 km) southwest of Galveston, Texas. Upon moving ashore, the hurricane had winds estimated at 130 mph (215 km/h) and a barometric pressure of 940 mbar (hPa; 27.76 inHg); these values were estimated using a peripheral pressure of 953 mbar (hPa; 28.14 inHg) measured at Velasco, Texas. At the time, the pressure measured at Texas landfall was the lowest ever measured in the United States. After moving inland, the storm quickly weakened, passing southwest of Houston, Texas, as a Category 1 hurricane before diminishing to a weak tropical storm within a day of landfall. Concurrently, the storm began to slowly curve towards the north and northeast, moving into northeast Texas on August 18. Two days later, the system transitioned into an extratropical cyclone while tracking northeast across Arkansas and southeastern Missouri; fronts extended outward from the cyclone's center. This trajectory continued before the storm's remnants were last noted in the Gulf of Saint Lawrence; HURDAT, the official database of storm paths in the Atlantic, indicates the storm dissipated after 18:00 UTC on August 23.
The United States Weather Bureau began issuing notices warning of the storm's presence on August 10, with information first sent to the Caribbean islands, followed by distribution to the Weather Bureau's stations along the Gulf and Atlantic coasts of the United States via their Arlington, Virginia, radio station. Initial forecasts predicted that the storm would cross Hispaniola and southeastern Cuba, but these landfalls did not materialize. Later anticipating that the hurricane would cross western Cuba, the Weather Bureau issued a northeast storm warning for Key West and Miami, Florida, on August 13. These warnings were briefly elevated later that day to hurricane warnings and extended northwards along to the Florida coast to Boca Grande. While these warnings were scaled down after the hurricane moved away from the state, falling pressures throughout the U.S. Gulf Coast on August 15 led the Weather Bureau to issue storm and hurricane warnings along the U.S. coast from Brownsville, Texas, to Apalachicola, Florida, eventually narrowing in extent to the Texas coast as landfall drew nearer. The head of the bureau's local office in Galveston, Texas, W. P. Stewart, cited the warnings as the sole reason for the relatively low number of fatalities in unprotected areas of the city.