Hurricane Bertha was on course to pass midway between Bermuda and the US East Coast on Monday and it was not expected to make landfall in either place, forecasters said.

Bertha strengthened to become the second hurricane of the Atlantic storm season and was wending its way toward the southwest at about 18 miles (30 kilometers) per hour.

"On the forecast track, Bertha will continue to move away from the Bahamas today and pass about midway between the US east coast and Bermuda on Tuesday," the National Hurricane Center said.

At 2100 GMT, the category one hurricane was 560 miles (900 kilometers) southwest of Bermuda, packing maximum sustained winds of 75 miles (120 kilometers) per hour.

Bertha is expected to drop up to five inches (13 centimeters) of rain across eastern portions of the Dominican Republic, as well as the Turks and Caicos through Monday.

Dominican authorities on Sunday declared a red-alert emergency after heavy rains triggered by Bertha toppled trees and flooded the banks of many rivers in the mountainous nation.

No injuries were immediately reported.

The 2014 Atlantic hurricane season, from June 1 to November 30, is expected to be quieter than usual, the NHC has said, with eight to 13 tropical storms -- of which three to six could rise to hurricane strength.

The year's first hurricane, Arthur, swiped the Atlantic seaboard over the July 4 holiday weekend, prompting evacuations in some places with its big waves, strong tidal surges and up to six inches of rain.

Meanwhile, another hurricane, dubbed Iselle, was updated to a category 4 storm with sustained winds of 140 miles an hour as it churns in the Pacific.

Iselle was on track to pass just north of the Hawaiian of Oahu on Thursday, although forecasters expect it to weaken.