The U.S. National Hurricane Center in Miami says the storm could become a hurricane by Sunday. Igor remained far from land and was about 465 miles (750 kilometers) west of the Cape Verde Islands.
The storm's maximum sustained winds Friday were near 40 mph (65 kph). It was moving to the west at 16 mph (26 kph).
Igor formed Wednesday off the coast of Africa near the Cape Verde Islands.
In Texas, four people are dead and three others were still missing Friday after the, causing flooding that swept away cars and overpowered swimmers in the Guadalupe River.
Officials planned to resume their search Friday for a missing swimmer and two motorists.
Authorities on Thursday recovered the body of Derek Joel-Nelson Clemens, 23, of Baldwin, Mich., from the Guadalupe River in New Braunfels. Floodwaters Wednesday had swept him and friend Nikos Paraskevopoulos, 28, of Alexandria, La., as they swam. Clemens' friend was still missing when the search was suspended for the night Thursday, and search officials hold dim hopes of finding him alive.
Two Texas motorists also are missing, officials said. Calvin Gibson, 57, was swept away near San Antonio when he tried to drive over a flooded creek, Bexar County spokeswoman Laura Jesse said. Authorities also continued to search in Austin for a woman whose sport utility vehicle was swept off the road by swollen Bull Creek.
Hermine caused relatively few problems when it made landfall as a tropical storm Monday night, but as the remnants moved north into Texas and Oklahoma, the flooding caught some people off guard. The sudden flooding in Texas on Wednesday led to more than 100 high-water rescues.
A 49-year-old man drowned after driving his pickup truck into a flooded crossing near Alvarado, and another person died in a vehicle submerged by water from a swollen creek near Austin, the National Weather Service said.
In eastern Oklahoma, a 19-year-old man drowned after his vehicle was swept off the road early Thursday. The Oklahoma Highway Patrol said it's unclear whether Jackie Warford was thrown from his vehicle or crawled out to try to swim to safety, but he became tangled in brush.
Pointing out that many of the dead and missing were swept away in their vehicles, Texas Gov. Rick Perry urged people not to try to cross swollen creeks or flooded roadways.
Hermine was the third tropical system this year to hit the Rio Grande Valley, a flood-prone area that encompasses northeastern Mexico and southeastern Texas.