Hurricane Earl slightly diminished in strength overnight but shifted to make landfall in the St. Margarets Bay area near Halifax, threatening to topple trees and down power lines as the storm barrelled through the Maritimes.

The storm, which forecasters called a marginal hurricane, brought strong winds and periodic sheets of rain throughout parts of Nova Scotia on Saturday morning.

"It's weakened a little," said Bill Appleby of the Canadian Hurricane Centre. "One thing that's changed overnight is we actually have a little bit more of a defined eye."

Appleby said that meant winds around the centre of the storm won't weaken as much as initially expected, fuelled in part by air and sea temperatures warmer than normal.

He said Earl was expected to make landfall in the early afternoon in the St. Margarets Bay area, west of Halifax, before curving up towards Pictou County in central Nova Scotia and Cape Breton.

Power outages were spreading across southern Nova Scotia, including Halifax, and the Annapolis Valley as the storm progressed.

As of 9 a.m. local time, Earl was about 100 kilometres off the southern tip of Nova Scotia, packing maximum sustained winds of 120 km/h. It was moving northeast at 52 km/h.

Forecasters warned that signs, tree branches and utility lines could be knocked down, causing further power failures.

RCMP said the road to the popular Peggy's Cove tourist site near Halifax was closed to keep curious storm-watchers away from the dangerous, pounding surf.

Over the years, there have been a number of fatalities involving people who were swept off the rocks and into the churning seas.

There were also numerous flight cancellations at airports across the Maritimes.