Hurricane Helene continued to gain strength as a Category 3 storm Monday, potentially threatening Bermuda at the end of the week, while a tropical storm watch was issued in the Azores as Hurricane Gordon churned in the Atlantic.

It was too soon to tell whether Helene would hit Bermuda, but the storm with top sustained winds of 125 mph was expected to be near the island Friday, said Chris Landsea, a meteorologist with the National Hurricane Center in Miami.

Helene strengthened late Sunday into the second major hurricane of the Atlantic season with 115 mph winds and intensified even more early Monday. Major hurricanes are those Category 3 and higher.

At 5 p.m. EDT, it was centered about 870 miles east-northeast of the northern Leeward Islands and about 1,015 miles east-southeast of Bermuda. It was moving northwest at 9 mph and was expected to continue on the same path into Tuesday, forecasters said. No significant change in strength was expected in the next day.

Visit FOXNews.com's Natural Disasters Center.

Meanwhile, Gordon was in the open Atlantic, centered about 960 miles west of Terceira in the Azores and moving northeast near 22 mph. Gordon had top sustained winds near 90 mph.

Gordon was expected to weaken, but forecasters have said watches or warnings could be issued as a precaution. Even if it did become an extratropical storm that gets energy from colliding weather fronts, it could still have tropical storm force winds.

The watch means tropical storm conditions are possible in the Azores in the next 36 hours.

The National Hurricane Center's latest forecast for the Atlantic season expects between seven and nine hurricanes, a slight reduction from earlier predictions.

Scientists have said that weak El Nino conditions had inhibited hurricane development by bringing higher ocean temperatures that increase crosswinds over the Caribbean. The winds can rip storms apart or stop them from forming.

But the National Oceanic and Atmospheric Administration has warned that the El Nino effect on hurricanes has been small so far. And the season, which lasts until Nov. 30, is still at its traditional peak.