Large swells have battered the northeast Caribbean as Hurricane Lee churned nearby through open waters as a Category 2 storm.

The storm, which is not forecast to make landfall, was centred about 455km northeast of the northern Leeward Islands. Its maximum sustained winds had decreased to 165km/h and it was moving west-northwest at 15km/h.

Earlier this week, Lee grew from a Category 1 storm to a Category 5 storm in just one day amid warm waters and limited wind shear.

"This was one of the fastest rates of strengthening in the Atlantic Basin on record," AccuWeather said in a statement.

Lee is expected to regain some strength on Sunday and Monday, according to the National Hurricane Centre.

The storm was forecast to pass well north of Puerto Rico the British Virgin Islands, which are still recovering from hurricanes Irma and Maria that hit in September 2017.

Tropical storm conditions were not expected for any Caribbean island, but breaking waves of up to five metres were forecast for Puerto Rico and nearby territories, with authorities warning people to stay out of the water.

"We are concerned about people and boaters who may underestimate the impacts of this passing storm," said Captain Jose Díaz of the Coast Guard sector in San Juan, Puerto Rico.

"The increase in projected sea states of (up to five metres) severely reduces our ability to respond to a maritime distress with the full use of our resources."

The National Hurricane Centre said the seas near the centre of the hurricane were expected to peak at 14 metres.

It noted that dangerous surf and rip currents were expected to hit most of the US East Coast starting Sunday, but that the hurricane's impact beyond that is still unclear.

"It is way too soon to know what level of impacts, if any, Lee might have along the US east coast, Atlantic Canada, or Bermuda late next week," the NHC said.

Meanwhile, officials in the French Caribbean island of Guadeloupe warned of up to 8mm of rain in a span of three hours or less for some areas, while officials in the French territories of St. Barts and St. Martin said flooding in some coastal areas was possible.

Lee was forecast to take a northward turn by Wednesday. However, its path after that remained unclear.

"Right now, the area in the United States that really needs to pay attention includes locations from the upper part of the mid-Atlantic coast to New England," said AccuWeather meteorologist Bernie Rayno.