(CNN) All eyes are on Hurricane Florence and its path toward the Carolinas, but other hurricanes and tropical storms are brewing as well. And the timing couldn't be more apt: Monday was the peak of the Atlantic hurricane season, when storm activity has historically been at its highest.
The National Hurricane Center downgraded Isaac to a tropical storm overnight but said Tuesday that it could be "at or near hurricane levels" on Thursday, when it approaches the Lesser Antilles Islands.
Winds of tropical storm strength could reach Puerto Rico on Friday morning. Tropical storms generate winds between 39 and 73 mph, just below hurricane force.
The storm is expected to produce 3 to 5 inches of rain across Martinique, Dominica, and Guadeloupe, with near 10 inches possible in isolated areas, forecasters said. Hurricane watches were in effect on those islands.
Tropical storm watches were in effect Tuesday for Antigua, Montserrat and St. Kitts and Nevis.
Still closer to Africa than North America, Hurricane Helene is predicted to head northeast in the Atlantic, then veer toward Europe, the center said.
Sustained winds on Tuesday afternoon approached 105 mph, making it a very strong Category 2 storm, though it was expected to gradually weaken over cooler waters. No coastal watches or warnings were in effect.
Meanwhile in the Pacific, Tropical Storm Olivia was close to Hawaii, where tropical storm warnings and watches are in effect, according to the Pacific Hurricane Center.
Gradual weakening is forecast during the next 48 hours, but Olivia is expected to remain a tropical storm as it moves over the main Hawaiian Islands.
CNN meteorologist Taylor Ward said the main threat will be flooding, with predictions of 5 to 10 inches, with isolated totals of 15 inches.
Olivia's maximum sustained winds are about 60 mph, after the storm weakened from Category 1 strength, forecasters said. Although Olivia is expected to move over the islands as a tropical storm, it could still bring worse impacts than recent Hurricane Lane to some areas, the center said.
National Weather Service officials in Honolulu urged residents to remain careful, noting that the difference between a Category 1 hurricane and a tropical storm is just 5 mph wind speed. Damaging winds, floods, high surf and storm surge are still possible.
Local governments closed some offices and warned residents to be prepared.