San Juan, Puerto Rico ? Tropical Storm Chris swept through the eastern Caribbean on Wednesday, forcing cruise ships to change course and tourists to evacuate small islands off the coast of Puerto Rico as it threatened to become the first hurricane of the Atlantic season.

The storm had top sustained winds of 60 mph as it moved west-northwest past Puerto Rico and the U.S. and British Virgin Islands. Outer bands of the swirling storm began to dump heavy rains on the U.S. Virgin Islands Wednesday evening.

A hurricane watch was issued in the southeastern Bahamas and the Turks and Caicos Islands, the National Hurricane Center said. The watch meant hurricane conditions of winds of at least 74 mph were possible by late today.

Some 600 tourists evacuated Culebra and Vieques, islands off Puerto Rico’s east coast.

“Everybody left,” said Jacinto Jiminez, owner of a hotel on Culebra.

The center of the storm was about 100 miles north-northeast of St. Thomas in the U.S. Virgin Islands Wednesday night. The storm was generally moving toward the west-northwest at 8 mph, forecasters reported.

The dark clouds and outer rain bands of Tropical Storm Chris are pictured just before sunset at the Old San Juan wall in Puerto Rico. Chris swept through the eastern Caribbean on Wednesday, skirting several islands but forcing cruise ships to change course and tourists to evacuate small islands.

Forecasters said it was likely to strengthen and could hit anywhere from south of Cuba to Florida by late this weekend.

Royal Caribbean, the cruise line operator, said it was changing the itineraries of three ships – the Navigator of the Seas, the Explorer of the Seas and the Freedom of the Seas – to keep them clear of the storm.

“Royal Caribbean will continue to closely monitor weather conditions,” the company said.

Trevor Basden, senior meteorologist with the Bahamas’ National Emergency Management Agency, said he expected Chris to strengthen into a weak hurricane as it passed through the island chain. He said the storm was likely to reach the Bahamas on Friday morning.

There were no reports of major damage or injuries as the storm skirted the Leeward Islands.