A tropical wave that exited the coast of Africa on August 15, 1964, moved westward, not organizing into a tropical depression until around 890 miles (1432.3 km) east of Barbados on August 20–as reported by a Navy reconnaissance plane. It continued west-northwestward, quickly strengthening to a hurricane the next day with a minimum central pressure of 993 mb. Early in the afternoon of August 22, Cleo crossed Guadeloupe as a 115 mph (185 km/h) Category 3 hurricane. The hurricane continued to strengthen as it moved through the Caribbean Sea and reached its peak intensity of 150 mph (250 km/h) on August 23 while south of the Dominican Republic. It maintained that intensity for a day, bringing heavy rain and winds to Hispaniola. As Cleo passed south of Haiti on August 24, it veered northward momentarily, enough to move on to the Southwest Peninsula of Haiti. The circulation of the hurricane was greatly disrupted by the mountainous terrain of the island, quickly weakening the hurricane.