Tropical Cyclone Isaias was the ninth tropical cyclone in the 2020 Atlantic Hurricane Season. On 28 July it developed as Potential Tropical Cyclone Nine over the central Atlantic, to the east of the Leeward Islands. On 29 July, it was upgraded to a tropical cyclone while it was over the Caribbean Sea, to the south of Puerto Rico. On 30 July, it strengthened to a category 1 hurricane while it was to the north of the Dominican Republic.