Helene weakened and was no longer a hurricane Sunday as it moved through the open Atlantic, forecasters said.

Helene's top sustained winds were near 70 mph, below the 74 mph threshold for hurricane force winds but above the 39 mph winds needed to be classified as a tropical storm, according to the National Hurricane Center in Miami. Helene had 85 mph winds earlier Sunday.

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The storm was no longer considered "tropical," meaning one that gets its energy from steamy ocean waters. Extratropical storms feed on energy from the collision of warm and cold fronts.

Helene could spread gale-force winds over the sparsely populated Azores on Sunday, although it was expected to pass well to the north of the islands, forecasters said.

Tropical storm-force winds extended up to 430 miles from Helene's center as it becomes a large area of low pressure.

At 11 a.m. EDT, Helene was centered about 595 miles west-northwest of the Azores. It was moving northeast near 21 mph.

The Atlantic hurricane season began June 1 and ends Nov. 30. September is traditionally one of the busiest months of the season.