Hurricane Flora is among the deadliest Atlantic hurricanes in recorded history, with a death total of at least 7,193. The seventh tropical storm and sixth hurricane of the 1963 Atlantic hurricane season, Flora developed from a disturbance in the Intertropical Convergence Zone on September 26 while located 755 miles (1,215 km) southwest of the Cape Verde islands. After remaining a weak depression for several days, it rapidly organized on September 29 to attain tropical storm status. Flora continued to quickly strengthen to reach Category 3 hurricane status before moving through the Windward Islands and passing over Tobago, and it reached maximum sustained winds of 145 miles per hour (233 km/h) in the Caribbean.

The Saffir–Simpson hurricane wind scale (SSHWS) classifies hurricanes—which in the Western Hemisphere are tropical cyclones that exceed the intensities of tropical depressions and tropical storms—into five categories distinguished by the intensities of their sustained winds. This measuring system was formerly known as the Saffir–Simpson hurricane scale, or SSHS.