The hurricane center was also watching another tropical wave - this one far to the east in the Atlantic.
Portions of the coasts of Florida and Georgia will see 1 to 2 inches of rain.
The National Weather Service warned Floridians to take Humberto seriously should it form. "For the Bahamas, that's not good news".
The disturbance has maximum sustained winds of 30 miles per hour (48 kph) and is moving to the northwest at 2 miles per hour (3.2 kph).
"We're seeing plastic tarps go out all over the islands, and that's extremely important because now you've got another tropical storm coming", said Ken Isaacs, vice president of programs for USA relief organization Samaritan's Purse.
No storm surge is expected.
Even as more weather systems are headed their way, people in the northern Bahamas scan social media, peer under rubble, or try to follow the smell of death in an attempt to find family and friends - amid alarming reports that 1,300 people remain listed as missing almost two weeks after Hurricane Dorian hit.
The system was mostly stalled Friday as two disturbances in the upper-level wind patterns spit out by a low pressure system in the Gulf of Mexico held it back.
"There have been problems in the coordination of this aid due to the magnitude of this devastation", Minnis said, adding that he understands the deep frustration of those dealing with "bureaucratic roadblocks" and pledged to reduce the red tape and bring in more aid and extra personnel.
Tens of thousands of people in the Bahamas face a daunting task to clean up the destruction left by the hurricane, with an estimated $7billion worth of damage and bodies potentially buried under the rubble.
Beaufort County's weekend forecast includes a 20-30% chance for rain showers and thunderstorms on both Saturday and Sunday with temperatures in the high 80s down to the mid- 70s.
Rainfall: the system is expected to produce total rain accumulations of 2 to 4 inches through Sunday over the Bahamas and along the east coast of Florida north of west palm beach.
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