MIAMI (AP) — Rivers surged across a large section of the Dominican Republic on Thursday as a broad area of low pressure headed east to the Turks and Caicos Islands and the Bahamas, officials said.

The US National Hurricane Center in Miami said the system’s strongest winds were below tropical storm strength but that it could strengthen as it approaches Florida and the Gulf of Mexico over the weekend.

Nearly 4 inches (10 centimeters) of rain fell in the Dominican Republic and 19 of its 32 provinces were on alert as rivers rose rapidly and flooding was expected, said Francisco Olguin, a spokesman for the Dominican meteorological office.

Residents of areas at a high risk for flooding were advised to begin evacuations because of possible flooding, said Juan Manuel Mendez, coordinator of the Emergency Operations Center.

Authorities in the Turks and Caicos Islands and Bahamas said heavy wind and rain was expected in parts of both island chains through Thursday night and small boats were advised to stay in port.

Meanwhile, Tropical Storm Gaston, which weakened from a hurricane earlier Thursday, was out over the Atlantic, about 1,160 miles (1,865 kilometers) east-northeast of the Leeward Islands. It had maximum sustained winds of 70 mph (110 kph).

In the Pacific, Tropical Storm Lester was strengthening far off Mexico’s coast. The storm’s maximum sustained winds were near 50 mph (85 kph). Lester was expected to become a hurricane on Friday.

Lester was centered early Thursday about 465 miles (750 kilometers) south-southwest of the southern tip of Mexico’s Baja California peninsula and was moving west-northwest near 12 mph (19 kph).