Humberto, with maximum sustained winds of 85 mph, was about 360 miles west-northwest of the southernmost Cape Verde islands moving north at 12 mph, the National Hurricane Center in Miami said in its 5 p.m. EDT advisory.
No watches or warnings were posted.
Humberto is expected to pick up some speed over the next two days before making a turn toward the northwest, the center said. The hurricane could strengthen more Thursday before weakening Friday.
Hurricane-force winds extended outward up to 30 miles from center and tropical-storm-force winds extended outward up to 115 miles from the center.