Tropical storm Bertha aims for southeast Bahamas, Turks and Caicos islands

A surfer enters the water to take advantage of the high waves in San Juan, Puerto Rico, Saturday, Aug. 2, 2014. Bertha pushed just south of Puerto Rico on Saturday as it unleashed heavy rains and strong winds across the region.(AP Photo/Ricardo Arduengo) (The Associated Press)

Two women walk with the protection of an umbrella in Old San Juan, Puerto Rico, Saturday, Aug. 2, 2014. Bertha pushed just south of Puerto Rico on Saturday as it unleashed heavy rains and strong winds across the region. (AP Photo/Ricardo Arduengo) (The Associated Press)

This NOAA satellite image taken Friday, Aug. 1, 2014, at 1:45 p.m. EDT shows a mass of clouds associated with Tropical Storm Bertha near the Lesser Antilles with most of the clouds and rain displayed to the east of the storm center. Clouds are prevalent over the Bahamas with some scattered rain and thunderstorms. Scattered storms are occurring over isolated portions of Hispaniola and Cuba. (AP Photo/Weather Underground) (The Associated Press)

Tropical Storm Bertha aimed for the Bahamas and the Turks and Caicos islands early Sunday as its heavy rains and wind led to the cancellation of flights and caused power outages in parts of the Caribbean.

The storm had maximum sustained winds of 45 mph (75 kph), and slow strengthening was expected by Monday. Bertha was centered 70 miles (110 kilometers) east-southeast of Puerto Plata in the Dominican Republic and was moving northwest at 22 mph (35 kph) late Saturday night.

Tropical storm warnings were in effect for the southeastern Bahamas and the Turks and Caicos Islands. A tropical storm watch was in effect for the central Bahamas.

Bertha clipped the Dominican Republic's northeast coast late Saturday after passing just southwest of Puerto Rico earlier that day, dropping between 3 to 5 inches (8-13 centimeters) of rain, with isolated amounts of up to 8 inches (20 centimeters).

The director of the Dominican Republic's Emergency Operations Center, Juan Manuel Mendez, said there were no immediate reports of damage.

Rescue crews traveled to the country's east and northeast regions to help with evacuations if needed, while authorities banned vessels from operating along the country's east coast, which is popular with tourists.

"Our obligation is to make sure that no person, national or foreign, experience problems" because of the storm, said Mendez.

Antigua-based regional airline LIAT and Seaborne Airlines canceled several flights in the Dominican Republic and Puerto Rico.

Bertha caused nearly 39,000 power outages in Puerto Rico, most of them in the island's central mountainous region following more than 1,200 lightning strikes that occurred in the area Saturday afternoon, authorities said.

More than 3,000 households also were left without water, said Alberto Lazaro, director of the island's water and sewer company.

The storm forced some 220 people into several government shelters in Puerto Rico's southeast region, the majority of them international athletes participating in a youth baseball tournament.

The heaviest rains fell in Puerto Rico's southern and eastern regions, with authorities urging people to stay indoors.

Puerto Rico Health Secretary Ana Rius warned people to use mosquito repellent and install screens on open windows, noting that the number of mosquitoes is expected to multiply across Puerto Rico in upcoming days as a result of the rains. The U.S. territory is battling dengue cases as well as an epidemic of the mosquito-born chikungunya virus.

The storm brought some rain to a drought-hit area of southern Puerto Rico, but it was not yet known whether it rained enough to cancel strict water rationing measures that are scheduled to start on Wednesday, authorities said.

On Friday, Bertha passed just north of the French Caribbean island of Martinique, where it left 150,000 homes without power. The storm also left hundreds of people without power along Dominica's eastern region.

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Associated Press writers Ezequiel Abiu Lopez in Santo Domingo, Dominican Republic, and Carlisle Jno Baptiste in Roseau, Dominica, contributed to this report.