A tentative forecast track from the U.S. National Hurricane Center in Miami shows the storm could hit the U.S. Gulf Coast next week.
The warning means tropical storm conditions are expected on Grand Cayman in 24 hours or less.
Tropical Storm Ida, which was packing winds of 45 mph (75 kmh), was expected to approach the Yucatan Channel on Sunday. A tropical storm watch was in effect for the Yucatan Peninsula of Mexico from Punta Allen north to San Felipe, and for the Cuban province of Pinar Del Rio.
Ida was moving toward the north at about 8 mph (13 kmh). It was centered about 220 miles southwest of Grand Cayman Island.
