Earl weakened to a tropical storm from a hurricane late Friday night but was still expected to bring heavy rain and strong winds as it remained on course for the Maritimes.

The storm passed just off Cape Cod, Nantucket Island and Martha's Vineyard in Massachusetts on Friday evening.

Around 11 p.m. ET, Earl was 150 kilometres south-southeast of Nantucket with maximum sustained winds of around 110 km/h.

Despite weakening off New England, the storm was expected to hit the Maritimes on Saturday as a Category 1 hurricane, somewhere between southwest Nova Scotia and New Brunswick's Bay of Fundy coast.

Chris Fogarty, program manager of the Canadian Hurricane Centre, said Earl was tracking slightly eastward, making Nova Scotia's Digby Neck area the closest approach zone. Landfall is expected between mid-morning and late morning.

He said intense winds are expected in mainland Nova Scotia, Prince Edward Island, the Gulf of St. Lawrence and possibly southeastern New Brunswick.

On Friday afternoon, tropical storm warnings were extended to all of mainland Nova Scotia, Cape Breton, Prince Edward Island, Îles-de-la-Madeleine and the Fundy coast of New Brunswick, including Moncton and southeast New Brunswick.

Tropical storm watches have also been extended to Kent County in New Brunswick, including Kouchibouguac National Park.

Hurricane watches remain in effect for Lunenburg, Queens, Shelburne, Yarmouth and Digby counties of Nova Scotia, as well as Halifax and Halifax County.

Rainbow Haven Beach near Halifax on Friday shows the first hints of tropical storm Earl, which is expected to bring strong winds and heavy rain Saturday. (CBC)

A midday update from Environment Canada also warned of possible damage to signage, roofing materials or building siding. Wave impacts at the coast in the hurricane watch area could lead to some beach erosion and damage, but the storm's arrival time may be near low tide, the update said.

The worst-hit areas could see sustained winds of 80 kilometres an hour and gusts of 120 to 130 km/h, Fogarty said.

Environment Canada said most parts of mainland Nova Scotia and southeastern New Brunswick could see 50 to 70 millimetres of rain. And that rain could fall quickly: some areas may see as much as 25 mm fall in just one hour.

Big waves and pounding surf are expected along south-facing coastlines, but the greatest threat of storm surge is anticipated in southwest Nova Scotia and the southern Gulf of St. Lawrence, including the Northumberland Strait.

Bill Lawlor, director of disaster management for the Canadian Red Cross in the Atlantic region, said the organization decided to wait to see the impact of Earl before it mobilizes its volunteers.

"We've been meeting each and every day over the last several days trying to figure out should we pre-mobilize, pre-position some of our materials," Lawlor said. "And it would just be throwing a dart at a board trying to figure out where that would be."

He said the Red Cross can reach any community in the Atlantic region within hours.

Fogarty said what is impressive about the storm is its size. The size plus the warm air and waters in the Maritimes mean that keeping concerns high about hurricane-force winds is "the responsible approach."

With files from The Canadian Press