Hurricane Bertha leapt in intensity to a category 3 storm Monday, as it raged over the open waters of the Atlantic Ocean between the Caribbean and Bermuda.

Forecasters warned that Bertha, the first hurricane of the Atlantic season, could move towards Bermuda in the coming days.

The Miami-based U.S. National Hurricane Centre said the storm was still more than 1,000 kilometres from the nearest land but it already had winds in excess of 180 km/h. That made Bertha a category 3 hurricane on the Saffir Simpson scale, which is used to measure the intensity of tropical storms. the centre said in a news release.

Storms of that intensity typically cause tidal surges of up to four metres, and the gusting winds can destroy mobile homes and damage buildings, according to the Hurricane Centre's website. Coastal areas may also have to be evacuated, the site warns.

In the coming days, Hurricane Bertha is expected to turn in the general direction of Bermuda, a low-lying archipelago about 1,030 kilometres off the eastern shore of the U.S.

Forecasters urged Bermuda residents to keep an eye on the storm's progress, even though it's still too early to tell whether it will hit the island.

At 5 p.m. ET on Monday, Bertha was moving northwesterly at just under 20 km/h and fluctuations in both speed and wind intensity were expected over the next 24 to 48 hours, the weather centre said.

The storm season began early this year with the first named tropical storm, Arthur, forming a day before the official start of the season on June 1 and soaking Mexico's Yucatan Peninsula.

With files from the Associated Press