Humberto, with maximum sustained winds of 85 mph, was about 515 miles northwest of the Cape Verde islands, pushing north at 15 mph, the National Hurricane Center in Miami said in its 11 a.m. EDT advisory.
No coastal watches or warnings were in effect.
Humberto was expected to gradually shift toward the northwest and west-northwest with a slight reduction in speed during the next couple of days, forecasters said.
The Category 1 hurricane is forecast to lose some of its punch with a faster rate of weakening likely by Saturday.
Hurricane-force winds extended outward from the storm's center up to 35 miles. Tropical storm-force winds extended outward up to 175 miles from Humberto's eye.